Collision+Lab+Ashley+and+Chelsea

=1D Cart Collisions Lab= 9/22/2009 (Date of Most Recent Edits)


 * Participants**: Chelsea Hart, Ashley Murphy
 * Purpose**: The purpose of this lab is to confirm the law of conservation of momentum.
 * Lab Documents**: [[file:1D Collsions.doc]]

. **Sample Calculations:** Initial momentum= m*v ||
 * Brief Description of Experiment**: During this experiment we looked at videos of collisions occuring on a track with carts. We used loggerpro to set a scale and create an axis with data points, which we then drew a line of best fit through and found the initial and final velocities of both carts. The slope of the lines of best fit were the velocities. These velocities were then used for calculations including the various masses of the carts to find initial and final momentum of each cart and the total in each experiment. With the momentum we did an extension on the lab and determined elasticity or inelasticity of each collision through kinetic energy calculations. Here is one of the graphs we used. Note that 'm' is representative of the slope and should correspond with the initial and final velocities in this experiment.
 * Data:** Momentum Chart (top) and Kinetic Energy Chart (bottom)
 * // Initial Momentum Calculation // || The Initial momentum was found by multiplying the mass of the cart (in kilograms) by the initial velocity of the cart (found on the graph created).

KE=½*m*v^2 ||
 * //Kinetic Energy Conversion// || The Kinetic Energy is calculated by multiplying ½ times mass times velocity squared.

F*(change in) t = m*(change in) v ||
 * //Impulse Calculations// || Impulse is calculated by the change in momentum (mass times change in velocity).

Calculation//​ ||< The final momentum is calculated by multiplying the mass of the cart (in kilograms) by the final velocity (found on the graph created). Final momentum=m*v ||
 * //Final Momentum

Due to the calculations made using initial and final velocities found through the data collected on the videos, we were able to prove that the collisions did indeed conserve momentum. We determined that, due to possible human inaccuracy in measurement, as long as the initial moentum and final momentum were less then 15% different, they were valid as evidence proving the law of conservation of momentum. 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? //The collisions that had directions associated with them were 10 version 1, 7 version 1, and 4 version 2. These had directions associated with them because they had negative velocities, which meant they were moving left, whereas positive velocities would be moving right. All of the collisions involved moving right, but to show a negative velocity, which we would identify by noting that it was moving left, we only had three collisions.// 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 refuse the law of conservation of momentum. Explain why this is so. //The reason the data would still be able to support the law of conservation of momentum even if the scale was incorrect is because the data would be shown acording to the incorrect scale, which would still show a conservation of momentum, simply with different numerical values.// 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? //The best data would be collected just as the cart is pushed, it isn't yet being affected by gravity or friction, which is what causes it to slow down. If the data were collected immediately before the collision, the forces from the magnets in the carts would already be having an effect on both carts, which would give inaccurate data.// 5. Calculate the percent difference between the initial total kinetic energy and the final total kinetic energy for each collision. Which collisions had large percent changes in kinetic energy? 6. Examine the group's analysis to see how each collision was characterized (as elastic or inelastic). How can you tell if collision will be inelastic? //A collision will be inelastic if when the carts collide, one cart is pushed by the other and the cart that pushes it does not move, but the cart that is collided into does not take the speed of the other cart. Then, the collision does not conserve kenetic energy, and therefore, is inelastic.//
 * //Total Initial Momentum Calculation// || The total initial momentum of the experiment is found by adding the initial momentum values of both carts in that particular experiment. Total initial momentum= initial momentum (red cart) + initial momentum (blue cart) ||
 * Results:**
 * Lab Questions ** :
 * Conclusion ** :Our experiment produced reproducable results because even when the data was changed slightly, the answers were still as we had concluded. The results could also be reproduced easily be another person because of the method used. To reproduce the results, one would simply have to use the same scale of measurement. To improve the experiment, the change of how the numbers are rounded, if at all, would be made more accurate if they were rounded to more decimal points. Because of human error, not rounding at all would make a substantial difference in the results if even one number was different; and could possibly change the results if all of the numbers were changed by just a decimal place/number.