Collision+Report;+Stephanie,+JC,+Aaron

=//​//1D Cart Collisions Lab= Date of Publication (Date of Most Recent Edits)


 * Participants**: Aaron Locke, Stephanie Morse, JC Smith
 * Purpose**: The purpose of this lab is to confirm the law of conservation of momentum.
 * Lab Documents**: [[file:1D Collsions.doc]]

This experiment was entirely on the computer. Several different videos of different collisions were provided, and we were responsible for calculating the velocity, momentum, and mass for the objects involved in each seperate video. This was done by observing different videos through the tool "Logger Pro". It allowed us to use different tools to set scales, create graphs, observe slope, and specific details of the collision. Specifically, we broke up the experiment into three parts, determining mass, determining initial and final velocity, and determining momentum. Mass was simple; each cart weighs 250 grams, and addition weight was written on the board behind the collision. Velocity, initial and final, was the most complicated aspect of the lab. We used a tool on Logger Pro that could add a point on the video, for each frame, that then corresponded with a graph. Apart for the point tool, we used a "set a scale" tool that could help us use the graph to find velocity. And this was done by using yet another tool to create a line of best fit, which then could supply us with a slope. And we used the slope as velocity. Below is an example of the a graph and line of best fit, with slope that we used to determine velocity.
 * Brief Description of Experiment**:


 * Data**: Create a table (when appropriate) including all data collected or calculated during the lab. Be sure to include a heading for each column that includes the units of each measurement.

1.1 || Collision 2.1 || Collision 5.1 || Collision 7.2 || Collision 4.2 || Collision || 13020 g cm/s || 12450 g cm/s || 7850 g cm/s || 0 g cm/s || 15750 g cm/s ||
 * || Collision
 * Blue Mass || 250 g || 750 g || 250 g || 250 g || 250 g ||
 * Red Mass || 250 g || 250 g || 250 g || 250 g || 750 g ||
 * Blue Initial || 54.8 cm/s || 36.50 cm/s || 67.05 cm/s || 79.97 cm/s || 50.48 cm/s ||
 * Blue Final || 0 cm/s || 18.63 cm/s || 32.20 cm/s || 0 cm/s || -24.11 cm/s ||
 * Red Initial || 0 cm/s || 0 cm/s || 0 cm/s || -66.69 cm/s || 0 cm/s ||
 * Red Final || 52.08 cm/s || 49.80 cm/s || 31.40 cm/s || 0 cm/s || 21.00 cm/s ||
 * Blue Before Collision || 13700 g cm/s || 27375 g cm/s || 16762.5 g cm/s || 17742.5 g cm/s || 12620 g cm/s ||
 * Blue After Collision || 0 g cm/s || 1397.25 g cm/s || 8050 g cm/s || 0 g cm/s || -6027.5 g cm/s ||
 * Red Before Collision || 0 g cm/s || 0 g cm/s || 0 g cm/s || -16672.5 g cm/s || 0 g cm/s ||
 * Red After


 * Sample Calculations:** Describe or reproduce a single example for any calculations that are performed during the experiment (other than averaging). For example, if you use a distance and a time to calculate a speed, you should show:


 * //Momentum Calculation//

//Kinetic Energy Calculation

Speed Calculation// || Momentum was calculated by taking the velocity found by the slope, and the mass of the car and multiplying.

momentum = velocity x mass

KE = ½mv²

speed = distance / time || The coefficient of static friction was determined to be 0.45. This was calculated from a measured angle using Newton's first law as desribed in the calculations.
 * Results**: Describe the major result of the experiment and how you arrived at this result. Typically, this will refer back to the purpose. For example, if the purpose was to find the coefficient of friction, you would write:

1. Mometum is a vector quantity (it has a direction associated with it). This is relevant for some of the collisions you analyzed. Which ones and why? //The way momentum works, it can have a positive and negative result depending upon the direction an object moves. In our experiment, the track was set up in a way that the blue car moves to the right, which is positive. Depending upon the collision, it may keep moving with the red car forward (thus being positive) or the collision would cause it to move back towards the left, creating a negative momentum. Simply put, in this experiment, if the car went right it was positive, if the car went left it was negative.//
 * Lab Questions**:

2. Calculate the percent difference between the initial total momentum and the final total momentum for each collision. Which collision had the largest percent change in momentum?

//Collision One: 13700 - 13020 = 680 / 13700 = 4.9 %//

//Collision Two: 27375 + 13972 = 41347 / 2 = 20673.5 - 12450 = 8223.5 / 41347 = 19.8 %//

//Collision Three: 16762.5 + 8050 = 24812.5 / 2 = 12406.25 - 7850 = 4556.25 / 24812.5 = 18.36 %//

//Collision Four: 17742.5 - 16672.5 = 1070 / 17742.5 = 6.03 %//

//Collision Five: 15750 + 6027.50 = 21777.5 / 2 = 10888.75 / 15750 = 69 %//

3. If you had not correctly scaled the video (the scale line was drawn incorrectly, for instance), it would have no effect on your data's ability to support or refute the law of conservation of momentum. Explain why this is so.

//This would have no effect on the data's ability to support or refute the law of conservation of momentum because only the velocity numbers would change but they would be the same as the the velocities with the right scale just to a different scale. The scale does not change how much momentum there was it only changes how it is represented by velocity.//

4. You may have observed the carts slowing down as they moved across the track before the collision. Suppose you have two velocities for a cart; one just after it was pushed and one immediately before the collision. Which would be better to use to evaluate your prediction and why?

//We would choose to evaluate the velocity just before the collision because it is closer to the collision and when you originally push the cart there is the extra force that you exert on the cart and after time that wears off due to friction.//

5. Calculate the percent difference between the initial total kinetic energy and the final total kinetic energy for each collision. Which collision had large percent changes in kinetic energy?

//Collision 1.1: 37.538 - 33.9041 = 3.6339 / 37.538 = 9.7% Collision 2.1: 49.959 - 44.016 = 5.943 / 49.959 = 11.9% Collision 4.2: 31.8529 - 23.8036 = 8.0493 / 31.8529 = 25.3% Collision 5.1: 56.19625 - 25.285 = 30.91125 / 56.19625 = 55% Collision 7.2: 135.5345 - 0 = 135.5345 / 135.5345 = 100%//

Colisions 5.1 and 7.2 had the greatest percent differences.

6. Examine the group's analysis to see how each collision was characterized (as elastic or inelastic). How can you tell if a collision will be inelastic?

You can tell if a collision is inelastic if the total kinetic energy before the collision is different than the total kinetic energy after the collision. A collision is elastic if momentum and kinetic energy are conserved, and a collision is inelastic if only momentum is conserved. A way of being able to tell if a collision is going to be inelastic is if the cars stick together. This is an example because kinetic energy is obviously lost if the cars are moving at eachother at one point, and then neither of them are moving after they hit.

Our group believed that momentum would be conserved because of the discussions the class had before beginning the lab. Two out of the five collisions we observed displayed the tendency to conserve momentum. But collisions 2.1, 5.1, and 7.2 did not conserve momentum. It would have been naïve to believe that all the experiments would display the conservation of momentum. But we also had hoped that more than two would show what we were looking for. The obvious effects that could have caused this include outside forces that influence the car in the video. But after discussion, my group concluded to the thought that, that wasn’t what caused the bad results. Instead it was simple human calculation error. Momentum was not conserved in most cases when the masses of the cars were not the same. But one sped up and one slowed down, which is a conservation. The only problem with this lab was that we were forced to work with videos. I believe that actually performing our own tests would have been better.
 * Conclusion**:

To be assigned later.
 * Reflection:** (to be completed by each group member individually).

//Don't forget to link to your lab report from the lab reports page and to include a link to your lab report in your reflection.//