ID+Collisions

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


 * Participants**: Megan Fucci, Kristin Kozlowski
 * Purpose**: The purpose of this lab is to confirm the law of conservation of momentum.
 * Lab Documents**: [[file:1D Collsions.doc]]


 * Brief Description of Experiment**: Provide a short (one paragraph) description of what was done during this experiment (including the data collection that was done for you and a description of how you collected your data from the video). Supplement this description with images, video, etc. to make clear and interesting. A figure that shows how you collected data off of the graphs or data tables should be included along with rationale for doing this.

For this lab we began by choosing five different experiments to analyze. We chose: 6-1, 10-2, 2-1, 7-2, 9-1. We observed the videos and plotted the points to express the movement of each cart at various times. Then we set scales on each graph to get the units of measurements we needed and then changed the axis to make the data more accurate. Then on our graphs we found the line of best fit, for the beginning and ending velocities. We used the slopes of those lines to find the velocities. Next, we used the velocities we found and the masses of the cars to determine each cars initial and final momentum's. Then we made charts to organize all our data. (The graph below is from 7-2.)


 * 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.
 * 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:
 * //Speed calculation//

//Momentum Calculation//

//Kinetic Energy Equation// || The speed in meters per second was calculated by taking the measured distance in meters and dividing by the time elapsed in seconds. speed = distance / time

P = velocity(m/s) * mass(g)

KE = ½mv² || 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:

The momentum was conserved when the masses and velocities are equal. (As seen in our graph above) This is relevant for the cars that went backwards, because then they had a negative velocity. They were being pushed in the opposite direction. You can see this with: 6-1, and 10-2. It was relevant for those, because both of them had cars that started going in one direction but were then hit and went back in the opposite direction (closer to where they started). This creates a negative momentum. After calculating all five trials (6-1, 10-2, 2-1, 7-2, 4-1), all momentum's decreased except the blue car in trial 7-2. The blue car's momentum increased 100% to have a momentum of 0 from -168.95. Other than the one increase in momentum, the car that had the largest percentage was the red car in trial 10-2. The momentum decreased by 321%. This would have no effect on your data because the error was a constant. That means that it effected all data equally. Your measurements of velocity and position may be off, but the numbers would still show that momentum is conserved. As long as the error effects all the data equally the results of the data should support or refute the law of conservation of momentum as they would if the scale was correct. The velocity taken just before the collision would be the best one to take. This is because the velocity of the cart immediately after it is pushed most likely will not have reached it's peek yet and is not very reliable. The second velocity is the best one to use to evaluate the predication, because the cart's velocity has most likely already slowed down and you can prove that it is not equal to it's peek velocity. However, this information is probably not enough. If you really wanted to make your prediction concrete, it is best to have the peek velocity and the velocity immediately before the collision.
 * Lab Questions**:
 * 1) Momentum 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?**
 * 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?**
 * 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.**
 * 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?**


 * Conclusion**: A good conclusion will include:
 * A statement about whether you think that the experiment produced a valid and reproducible result and reasoning supporting your statement.
 * A suggestion as to why your experimental results differ from any accepted value or your expected result (if appropriate).
 * A suggestion for a simple improvement to the experiment. Think about what caused problems, measurement inaccuracies, or inappropriate simplifying assumptions and propose a change. A sketch may be helpful.

We thought that momentum would be conserved and some of our results showed that, but others did not produce expected results. 10-2, 2-1 and 4-1 didn't conserve momentum. I didn't expect all the experiments to conserve momentum, but I figured more would. Outside forces would impede the ability of the object to conserve momentum, but there were no outside forces (that I know of) that affected our experiments. Momentum wasn't conserved when the masses of the cars were different. We did see, however, that when one car lost momentum, by hitting the other car, the other car did gain momentum. Showing that some momentum was conserved. The cars that weighed the same were more likely to conserve momentum. It would have been kind of nice if we had gotten to do the experiments ourselves. I liked using the video and LoggerPro, but sometimes it's easier to do things hands-on.

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.//