Unit2_KoscielnyD

= Lesson 17 = toc

Vocabulary
phi= angle between force and direction of motion || N, T, or f along axis of movement || Scalar || moving || Scalar || Potential Energy || energy possessed by an object because it is above or bellow a relative 0 point (can be + or -) (it has the ability to fall) (sometimes it's better to make the end 0, not the ground) || GPE (PE sub g) u sub g || J || GPE=(mg)h h or y h&y are vertical position || location is above or bellow 0 location || Scalar || Energy || the energy possessed by an object due to a stretched or compressed spring (also bungee cords) || EPE (SPE, PE) || J || EPE= 0.5kx^2 k= spring force constant (tells you how springy your spring is) x= distance stretched or compressed || streched or compressed springy thing || Scalar ||
 * || Definition || Symol || Units || Equations || Cue || Type ||
 * Work || caused by force acting on the axis of the direction of motion (has to be moving) || W || Joules (J) || W=F*d*cos(phi)
 * Kinetic Energy || energy due to the motion of an object || KE || J || KE=0.5mv^2 || object is
 * Gravitational
 * Elastic Potential

Law of Conservation of Energy (LCE)
- Energy isn't created or destroyed, only transferred - Initial Energy= FInal energy - can only increase or decrease energy in a system using work (putting work in or taking work out of a system) - if object is falling, GPE should equal w (weight) - d= sinking in to surface

Air Bag Lab
__Objective:__ How does an air bag protect you during an accident? __Hypothesis__: it absorbs the impact of your head whipping forward. __Materials:__
 * 2 eggs
 * bowl filled with flour
 * meter stick
 * zip-lock bag
 * stopwatch
 * note: some days I just can't spell.

__Procedure:__ //Note: You may want to use the available technology to take "Before" and "After" pics to post in your data table to assist and elaborate on your written descriptions.//
 * 1) Measure the length of your egg #1. Measure the mass of your egg. Record this information.
 * 2) Place an egg in a ziplock bag, squeezing out all of the air in the bag before sealing.
 * 3) Hold a ruler up on the table vertically. Hold the egg vertically at the 2 cm mark. (Keep the excess bag on top.) Drop it.
 * 4) Hold the egg the same exact way at the 4-cm mark and repeat. Continue this process until the egg shell is slightly cracked.
 * 5) Continue until the egg is smashed and the yolk leaks out. Measure the amount of egg still undamaged. How much of the egg is smashed?
 * 6) Fill a bowl with flour and place the bowl inside of the box lid.
 * 7) Measure the length of your egg #2. Measure the mass of your egg. Record this information.
 * 8) Drop the egg from the smash height (Step 5). Measure the amount of egg sticking up out of the flour bed. How much of the egg is buried in the flour? Also, record your qualitative observations.
 * 9) Repeat this, increasing the height in 5-cm increments until the egg is cracked, and then smashed.

__Data and observations__:
 * || Egg Mass (kg) || Egg Length (m) || Drop Height (m) || Cracked or Smashed? || How much egg is buried (m) || Initial gravitational potential energy (J) || Work done (J) || Force Experienced by Egg (N) ||
 * Trial ||^  ||^   ||^   ||^   ||^   ||^   ||^   ||^   ||
 * max height || 0.0514   ||  0.055   ||  0.25   || Smashed ||   ||  0.126   || - ||  2.29   ||
 * 1  ||  0.05213   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.25   ||   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.001   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.128   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">-0.128   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">127.72   ||
 * 2  ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05213   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.3   ||   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.001   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.153   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">-0.153   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">153.26   ||
 * 3  ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05213   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.35   ||   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.006   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.179   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">-0.179   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">29.80   ||
 * 4  ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05213   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.4   ||   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.007   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.204   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">-0.204   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">29.19   ||
 * 5  ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05213   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.45   ||   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.01   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.230   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">-0.230   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">22.99   ||
 * 6  ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05213   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.5   ||   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.01   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.255   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">-0.255   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">25.54   ||
 * 7  ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05213   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.55   ||   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.015   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.281   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">-0.281   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">18.73   ||
 * 8  ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05213   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.6   ||   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.015   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.307   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">-0.307   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">20.43   ||
 * 9  ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05213   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.65   ||   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.016   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.332   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">-0.332   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">20.75   ||
 * 10  ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05213   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.7   ||   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.017   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.358   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">-0.358   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">21.04   ||
 * 11  ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05213   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.75   ||   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.018   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.383   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">-0.383   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">21.29   ||
 * 12  ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05213   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.8   ||   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.019   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.409   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">-0.409   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">21.51   ||
 * 13  ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05213   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.85   ||   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.021   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.434   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">-0.434   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">20.68   ||
 * 14  ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05213   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.9   ||   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.022   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.460   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">-0.460   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">20.90   ||
 * 15  ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05213   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.95   ||   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.017   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.485   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">-0.485   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">28.55   ||
 * 16  ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05213   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">1   ||   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.018   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.511   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">-0.511   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">28.38   ||
 * 17  ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05213   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">1.1   ||   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.019   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.562   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">-0.562   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">29.58   ||
 * 18  ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05213   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.05   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">2   ||   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">0.022   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">1.022   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">-1.022   ||  <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">46.44   ||

__Calculations:__ Show a sample for each, with equation(s), numbers plugged in, and answer with correct units. GPE=mgh GPE=0.05213*9.8*0.25 GPE=0.128J
 * What is the initial gravitational potential energy?

W= GPE W=mgh W=0.05213*9.8*0.25 W= 0.128J
 * How much work is done in each trial?

F= W/d F=mgh/d F=0.05213*9.8*0.25/0.0001 F=127.72N
 * How much force was used to stop the egg in each case?

__Questions:__ The egg represents the head of a person in the automobile, the table (or cement floor in our experiment) represents the dashboard and the flour represents the airbag stopping the "head" from being hurt by the "dashboard" Gravitational potential energy is an objects potential for kinetic energy due to its placement relative to a determined 0 value. Kinetic energy is the energy of motion an object has. Work is a (positive or negative) force acting on the axis of motion. Gravitational potential energy and work. If the work is opposite the direction of motion, as with friction, it decreases kinetic energy; however, if it is in the direction of motion, it increases it. Impulse would stay the same and because impulse is force*time, the longer the time, the lesser the force. It makes the impulse less forceful, often sparing the passenger injuries. It increases time of impact, thus decreasing force. energy must stay the same even if time of impact changes, so something else (force) has to change to equalize the equation.
 * This investigation is an analogy for a person in an automobile collision. What does the egg represent? What does the table represent? What does the flour represent?
 * Define the terms: Gravitational Potential Energy, Kinetic Energy and Work.
 * What factors determine an object's kinetic energy?
 * When work is done on an object, what is the effect on the object's kinetic energy?
 * How does the force needed to stop a moving object depend on the distance the force acts?
 * What difference does a soft landing area make on a passenger during a collision?
 * How does a cushion reduce the force needed to stop a passenger?
 * What does the law of conservation of energy have to do with this?

__Conclusion:__ Because of the law of conservation of energy, Mass and change in velocity must stay the same regardless of time of impact, so when the time of impact gets greater, force must get smaller to compensate. Measuring how much of the egg was out of the flour had great potential for error because the egg was usually slightly horizontal (as it was impossible to get it to fall completely vertically) and the angle of the egg would have always been slightly different, and thus the total height would have been slightly different. If we dropped the egg at greater intervals (going 20 cm rather than 5 to 10 up each time) we could use the extra time to make sure the egg fell similarly each time.
 * Using the law of conservation of energy, explain how an air bag can protect you during an accident. Use specific observations from this investigation to support your answers to these questions.
 * Explain at least 1 cause of experimental error. Be sure you describe a specific reason.
 * How would you improve the results of this lab? (In other words, what would you change about the materials or procedure to eliminate or reduce the experimental error you describe above?)

= Homework = **Reading Summary:** Q: What does "work" mean in physics in words and mathematically? A: - force causes a displacement (To clarify, a **specific force** must be **making** the object move) - (F= force, d=displacement, theta= angle between F and d vectors) - for "negative" (displacement hindering) work, theta is 180 Q: how do you find the amount of work done? A: plug the three variables in to the equation, keep in mind that more than one force can be doing work Q: What is Potential energy and how do you find it? A:- Energy of position: energy due to distance from some decided 0 point - Gravitational: **PEgrav = m • g • h** - Elastic: Q: How do you define and solve for kinetic energy: A:- Energy of motion - to calculate: - Joules are the unit for force: Q: What is Mechanical Energy: A:- the sum of potential energy(s) and kinetic energy(s)
 * Definition and Mathematics of Work**
 * -** When F and d are in the same direction, theta=0
 * Calculating the Amount of Work Done by Forces**
 * Potential Energy**
 * Kinetic Energy**
 * Mechanical Energy**

Q: What is power? A:- The work/time ration measured in watts
 * Power**

**Joke:** A physics student was hit by a brick falling from a house. He fainted, but came to after a while and started smiling. The onlookers were worried, so they asked him why the smile. "I just realized how lucky I am because the kinetic energy is only ** half ** m v squared." URL:[]

= Lesson 18 =

Energy
- most energies are path independent, work is not

Homework
**Reading Summary:** Q: What's the difference between internal and external forces? A: - Internal: spring, gravity, magnetic, electrical - External: applied, normal tension, friction, air resistence - depends on ability to change an objects total mechanical force: external changes,internal does not - total force is always conserved Q: How do you calculate external force? A: - external forces= non-conservative forces b/c they change the total mechanical energy of an object - relationship between mechanical energy and force: **TMEi + Wext = TMEf**, where **TME** = **KE + PE**
 * Internal vs External Forces**
 * Analysis of Situations Involving External Forces**

- EX.

Q: how do you calculate internal force? A:- for internal forces, **KEi + PEi = KEf + PEf** because force is conserved - EX. (also, consider the movement of a pendulum) Q: How do Bar Charts represent energy transfer A: The heights of the bars show how much energy is conserved and what forces the energy is from, EX. = Lesson 19 =
 * Analysis of Situations in Which Mechanical Energy is Coserved**
 * Aplication and Practical Questions**
 * Bar Chart Results**

Power
>
 * the rate of energy **dissipation** (usage)
 * rate=something/time
 * P=W/t
 * P= (Fd)/t = Fv
 * ^ average on constant speed, no acceleration
 * Watts (W) WRITE IT OUT b/c W is confuzzling
 * horsepower (hp) is a measurement of power- 746 watts

Momentum

 * "quantity of motion"
 * Momentum=p=m*v
 * the relationship between mass and velocity- think about how much inertia there is- an object in motion will stay in motion and it's harder to get more massive object to stop being in motion
 * kg*m/s
 * netF=ma=m(delta v/delta t)
 * netF*detlat t= m*delta v, impulse (J) =change in motion, N*s=kg*m/s
 * to get a ball you it it faster- you increase force (netF) or follow through (greater delta t)
 * if the momentum is the same, you want time to be greater so force will be less- that's why the give in seat belts and the airbag (the deflation when you hit the bag saves you- increase of time of impact)
 * "roll with the punches"- step with punch so the time is increased and force is decreased
 * Impulse- do without thinking and has big impact
 * MOMENTUM IS A VECTOR

Momentum and Elastic Collisions Lab:
__Objective:__ A small sports car hits a heavy truck in a collision. What factors determine the outcome for the passengers of the two vehicles? Which driver will sustain worse injuries? Why? __Materials:__ List any materials used and draw a labeled diagram of your set-up (alternatively, include a snapshot or video). __Procedure:__
 * 1) Place a cart on the middle of the track with the spring to the right. On a piece of masking tape, label this the "Target cart." Place a second identical cart on the right end of the track. Mark this as the "Bullet cart".
 * 2) Push the bullet cart very gently towards the target cart so that they collide, with the spring between them.
 * 3) Repeat step 2 several times, giving the bullet cart a bigger push each time. Record your observations.
 * 4) Add 500-g to each cart and repeat the process. Record your observations and compare the results to the first set of collisions.
 * 5) Remove the mass from the target cart and repeat the above steps.
 * 6) Add the mass to the target cart and remove the mass from the bullet cart, and repeat.
 * 7) Get the "Mystery" cart from your teacher. Determine the relative mass of the cart by putting it through a sequence of collisions.

__Data and observations:__ __Questions:__ It could represent bumper cars hitting each other and bouncing (accelerating) back. We were able to predict the weight very accurately by trying to make the mass of the bullet cart equal to that of the cart with the mystery weight on it They had less velocity and covered less distance as the masses were greater and the force applied stayed the same. Momentum is the type of inertia that keeps an object moving, it is dependent on mass and volume. The eagle has greater momentum because it has greater mass. On impact, one object pushes the other, transferring the velocity. Being far less massive than the car, the skateboarder would be pushed backwards with great acceleration; being more massive,the car might accelerate negatively, but in comparison only a little as the force would not be great in comparison to the mass and velocity.
 * B= bullet cart**
 * A= target cart**
 * Trial # || Mass of Bullet Cart (kg) || Mass of Target Cart (kg) || Applied force (qualitative only) || Description and Observations (qualitative) ||
 * 1 || .5 || .5 || Very gently || B hit A, B stayed still and A bounced back against the wall, and bounced forward, hitting B so B slowly slid back to the other wall ||
 * 2 || .5 || .5 || Gently || “1”, only faster ||
 * 3 || .5 || .5 || Medium || “2”, only faster ||
 * 4 || 1 || 1 || Very gently || “1”, only they moved more slowly and because A didn’t bounce back as hard, ||
 * 5 || 1 || 1 || Gently || “1” only a tiny bit slower ||
 * 6 || 1 || .5 || Very Gently || A moved faster than B as it bounced back ||
 * 7 || 1 || .5 || Gently || B bounces a little when hit back by A after A bounces ||
 * 8 || 1.5 || .5 || Gently || After A bounces back it barely bounces B in the middle ||
 * 9 || .5 || 1 || Gently || B bounces back ||
 * Mystery Car Weight # || Estimated/ Experimental (kg || Real (kg) ||
 * 1 || 0.75 || 0.7 ||
 * 2 || 1.23 || 1.2 ||
 * What is a real-life collision that the collisions in this investigation could represent?
 * How well did observing collisions enable you to compare the masses of the carts in the last step?
 * What happened after the collision as the masses changed?
 * Define the term momentum.
 * Which object has greater momentum, a butterfly traveling at 16 km/h or an eagle traveling at the same speed?
 * How does the transfer of momentum occur?
 * Use momentum to describe what would happen if a skaterboarder was hit by a car.

__Conclusion:__ · Based on the relative amounts of momentum, what is the outcome of a head-on collision between a heavy truck and a small sports car if both have the same speed? The truck (rightward) would have a small negative acceleration and the car (originally leftward) wold have a greater positive acceleration.

· Explain at least 1 cause of experimental error. Be sure you describe a specific reason. This lab was very qualitative so the "data" depends on how constant the speed we pushed the cart at was, how we saw the collision (as in what angle we were viewing from), and how well we were able to remember and compare to previous tests. judging by how accurate our guess was for the mystery masses, we were fairly accurate in our observations, even though our method was not precise.

· How would you improve the results of this lab? (In other words, what would you change about the materials or procedure to eliminate or reduce the experimental error you describe above?) We could use a mechanism to make the force the cart was pushed at constant or measurable, and we could measure where the carts ended up at rest.

Homework
**Reading Summary:** S= summary TS= Topic sentence S:
 * Momentum**
 * Momentum = mass*velocity
 * p=mv
 * measured in kg*m/s
 * vector quantity
 * p of an object at rest=0

TS: Momentum, the product of mass and velocity, can be used to guide thinking as well as to find quantitative values; if you consider the equation you find that the objects at rest must have no momentum and if you double mass OR velocity, momentum will be doubled.

S:
 * Momentum and Impulse Connection**
 * Equations derived from the original

**or:**



TS: When finding variables for objects that have collided, as in an elastic collision, you can can use a variety of derived equations, depending on the variable you are looking for,
 * Impulse (F*t) =Change in momentum
 * both objects in a collision experience the same force, momentum, and impulse, the less massive one experiences more acceleration
 * Elastic collision- objects rebound with the same momentum as they had before the collision

S: TS: It is important to understand the factors that determine force because each variable plays a part in determining the situation.
 * Real-World Application**
 * The larger the collision time, the smaller the force because Ft=m(delta]v
 * if an object rebounds it has a greater change in force than if it crumbles into or pushes whatever it collides into

**Cartoon:** = Lesson 20 =

Law of Conservation of Momentum

 * Momentum cannot be created or destroyed but can be transferred
 * Total momentum of a system is constant as long as the system is isolated (ignoring friction during collision)
 * Momenta is plural

Momentum and Inelastic Collisions Lab
__Somewhat Irrelevant Objective__: What physics principles do the traffic-accident investigators use to "reconstruct" the accident? __Somewhat Irrelevant Hypothesis__: The weight of the cars, the speed of the cars, and the friction of the road. __Objective__: How does the initial momentum relate to the final momentum of the cart? __Hypothesis__: The more initial momentum there is, the more final momentum there will be. __Procedure:__
 * 1) Place 2 photogates on a track, one at 50 cm and the other at 75 cm. Hook these into a Smart Timer and set the Smart Timer to Velocity.
 * 2) Place a cart so that its end is at 75 cm (right in front of the photogate), with the velcro facing 0-cm. Call this the "target cart." Place a second identical cart at the end of the track closest to 0-cm. Call this the "Bullet cart". Make sure that both carts have picket fences.
 * 3) Click "Start" on the Smart Timer, and then push the Bullet cart very gently towards the Target cart so that they collide and stick together. You may need to practice this a few times.
 * 4) Record the velocity right before (the Bullet Cart initially) and right after the collision (the two carts linked). Record these values in your data table.
 * 5) Vary the masses of the carts and repeat the process 5 times.

__Data and observations:__
 * <span style="color: black; font-family: 'Times New Roman',serif; font-size: 12pt;">Mass of Bullet Cart (kg) || <span style="color: black; font-family: 'Times New Roman',serif; font-size: 12pt;">Mass of Target Cart (kg) || <span style="color: black; font-family: 'Times New Roman',serif; font-size: 12pt;">Speed of Bullet Cart (m/s) || <span style="color: black; font-family: 'Times New Roman',serif; font-size: 12pt;">Speed of Target cart (m/s) || <span style="color: black; font-family: 'Times New Roman',serif; font-size: 12pt;">Combined masses (kg) || <span style="color: black; font-family: 'Times New Roman',serif; font-size: 12pt;">Final Velocity of both carts (m/s) ||  || <span style="color: black; font-family: 'Times New Roman',serif; font-size: 12pt;">Initial Momentum kgm/s || <span style="color: black; font-family: 'Times New Roman',serif; font-size: 12pt;">Final Momentum kgm/s || <span style="color: black; font-family: 'Times New Roman',serif; font-size: 12pt;">% Differences ||
 * <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.5 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.5 || 0.083 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: center;">0 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1 || 0.04 ||  || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.0415 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.04 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">3.61% ||
 * <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.5 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.5 || 0.066 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: center;">0 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1 || 0.031 ||  || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.033 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.031 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">6.06% ||
 * <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.5 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.5 || 0.083 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: center;">0 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1 || 0.041 ||  || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.0415 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.041 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1.20% ||
 * <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.5 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.5 || 0.072 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: center;">0 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1 || 0.034 ||  || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.036 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.034 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">5.56% ||
 * <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.5 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.5 || 0.083 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: center;">0 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1 || 0.04 ||  || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.0415 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.04 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">3.61% ||
 * <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.5 || 0.053 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: center;">0 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1.5 || 0.033 ||  || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.053 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.0495 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">6.60% ||
 * <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.5 || 0.047 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: center;">0 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1.5 || 0.029 ||  || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.047 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.0435 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">7.45% ||
 * <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.5 || 0.063 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: center;">0 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1.5 || 0.04 ||  || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.063 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.06 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">4.76% ||
 * <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.5 || 0.038 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: center;">0 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1.5 || 0.022 ||  || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.038 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.033 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">13.16% ||
 * <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.5 || 0.073 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: center;">0 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1.5 || 0.049 ||  || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.073 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.0735 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.68% ||
 * <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.5 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1 || 0.102 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: center;">0 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1.5 || 0.033 ||  || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.051 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.0495 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">2.94% ||
 * <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.5 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1 || 0.08 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: center;">0 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1.5 || 0.025 ||  || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.04 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.0375 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">6.25% ||
 * <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.5 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1 || 0.125 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: center;">0 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1.5 || 0.041 ||  || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.0625 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.0615 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1.60% ||
 * <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.5 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1 || 0.091 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: center;">0 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1.5 || 0.029 ||  || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.0455 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.0435 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">4.40% ||
 * <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.5 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1 || 0.125 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: center;">0 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1.5 || 0.041 ||  || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.0625 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.0615 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1.60% ||
 * <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1.5 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1 || 0.051 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: center;">0 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">2.5 || 0.029 ||  || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.0765 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.0725 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">5.23% ||
 * <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1.5 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1 || 0.047 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: center;">0 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">2.5 || 0.026 ||  || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.0705 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.065 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">7.80% ||
 * <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1.5 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1 || 0.092 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: center;">0 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">2.5 || 0.055 ||  || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.138 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.1375 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.36% ||
 * <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1.5 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1 || 0.052 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: center;">0 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">2.5 || 0.029 ||  || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.078 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.0725 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">7.05% ||
 * <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1.5 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1 || 0.05 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: center;">0 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">2.5 || 0.028 ||  || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.075 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.07 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">6.67% ||
 * <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1.5 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">1 || 0.05 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: center;">0 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">2.5 || 0.028 ||  || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.075 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">0.07 || <span style="color: black; display: block; font-family: 'Times New Roman',serif; font-size: 12pt; text-align: right;">6.67% ||

__Calculations:__ Show equation(s), numbers plugged in, and answer with correct units. Add columns in your data table to include these results. initial=m*v 0.5*.08=0.0415 kg*m/s
 * Find the initial momentum of the bullet cart for each trial.

initial=m*v 0.5*0=0
 * Find the initial momentum of the target cart for each trial.

initial+final=sum 0.0415+0=0.0415 kg*m/s final=m*v 1.0*0.04=0.04 kg*m/s %dif= |(calc3-calc4)/calc3| %dif= |(0.0415-0.4)/0.0415| %dif= 0.036 dif=3.6%
 * Find the sum of the initial momenta of the two carts for each trial.
 * Find the final momentum of the combined carts for each trial.
 * Find the percent difference between the initial momentum (calc 3) and the final momentum (calc 4).

__Questions:__ they are the same because momentum is conserved.
 * How do the initial momenta compare to the final momenta? Allowing for minor variations due to uncertainties of measurement, are there any patterns?

Collisions where kinetic energy is not conserved are inelastic- you know because the objects move together.
 * Which types of collisions are definitely inelastic? How do you know?

Collisions where KE is conserved are elastic- you know because the objects move in opposite directions or only one moves.
 * Which types of collisions are definitely elastic? How do you know?

The momentum from the first ball transfers to the other balls and because the combined mass of the other balls is much greater, the cue ball stops at the point of impact.
 * Use the law of conservation of momentum to describe what happens when a cue ball hits the 15 balls in the middle of the pool table.

__Conclusion:__ Though in cars the investigators must take the crumbling of the car into account as well, investigators can find the initial velocity of each car prior to the accident by using how far the cars traveled in what direction and the mass of each car and vice versa.
 * Based on the law of conservation of momentum, how can the traffic-accident investigators use this to "reconstruct" an accident? What does it mean to "conserve" momentum?

There wasn't much source of human error because the values were measured by the laser things, but one of the picket fences was paper and though it was a copy of the other fence, the paper could have bent a little throwing off the experimental velocity.
 * Explain at least 1 cause of experimental error. Be sure you describe a specific reason.

I would measure the actual mass of the carts including the picket fence things
 * How would you improve the results of this lab? (In other words, what would you change about the materials or procedure to eliminate or reduce the experimental error you describe above?)

Homework
**Reading Summary:** S=Summary TS= Topic sentence S/TS: Acceleration depends on force and mass so though the force is the same for 2 interacting objects, the acceleration is different.
 * The Law of Action-Reaction Revisited**

S: TS: Because of the law of conservation of momentum, momentum lost by one coliding object is gained by the object it colides with and vice versa.
 * Momentum Conservation Principle**
 * in a collision forces are equal but in opposite directions: F1=-F2
 * the time the forces are touching is equal for both
 * So...
 * thus...

S/TS: Net external force can also act on the system; if there are unbalanced forces, for instance, if there were significant friction and nothing to balance it, some momentum would be lost to the external forces.
 * Isolated Systems**

S/TS: It is sometimes unnecessary to solve for anything; for instance, you can find that if a moving object hits a stationary object of the same mass, they will continue to move at half the initial speed by simply exploring the equation and plugging in numbers.
 * Using Equations as a "Recipe" for Algebraic Problem-Solving** (just reviews problem solving)
 * Using Equations as a Guide to Thinking**

S/TS: Even in explosions, total Momentum evens out because if the explosion if vertical, the values are equal but opposite, and if it is in every direction, each direction cancels it's opposite direction. = = = Lesson 21 =
 * Momentum Conservation in Explosions**

Roller Coasters
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<span style="display: block; height: 1px; left: -10000px; overflow: hidden; position: absolute; top: 4345px; width: 1px;">__<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Objective: __<span style="font-family: 'Times New Roman','serif'; font-size: 12pt;"> A small sports car hits a heavy truck in a collision. What factors determine the outcome for the