Collision+Lab+Wagene+and+Rachelle

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


 * Participants**: Rachelle Chiasson and Wangene Hall
 * Purpose**: The purpose of this lab is to confirm the law of conservation of momentum.
 * Lab Documents**: [[image:http://www.wikispaces.com/i/mime/32/application/msword.png width="32" height="32" link="http://hartfordphysics.wikispaces.com/file/view/1D+Collsions.doc"]] [|1D Collsions.doc]


 * Statement of the Problem:** According to the law of conservation of momentum, __//For an isolated system (one that experiences no outside forces) the total momentum in the system is conserved, even if the momentum of a single object is not constant//__. The goal of this lab is to examine the validity of this law for the case of several one dimensional collisions that have been video taped. For this experiment, our prediction is that the law of conservation of momentum is true for carts colliding along one dimension.


 * Brief Description of Experiment**: This experiment was designed to obtain data pertaining to the mass of any object involved in the collision, the initial and final velocity of any object involved in the collision, and the total momentum before and after the collision. Dr. Pasquini performed and filmed collisions, five of which we used to collect and analyze our data. We used LoggerPro to collect data on the five collisions that were of interest to us. We set a scale for the first video collision that we chose, using a 61 cm leveling tool that was on the table at the time. We set our origin straight along the path of travel. We then plotted the position of the blue car for every frame. We continued this until the moment before the blue car collided with the blue car, at which time we took our initial velocity using the x-value of our graph right before the time of collision. We continued to plot the position of the blue cart after it was hit to get the final velocity of the collision.

After finding both initial and final velocities for the blue cart, we found those values for the red cart. With the exception of two collisions, the red cart did not begin in motion, having an initial velocity of zero. We used our graph of position and time to find velocity (taking the slope/derivative of position yields velocity) and our data (at t = x, when x represents either the velocity immediately before and after the collision. Our calculations lead to the conclusion that the law of conservation of momentum was, in fact, valid for this lab; meaning, the momentum was conserved between the two carts.


 * DATA COLLECTION:**


 * Procedure (Step by step description of how the data was analyzed)**

To find and analyze the data needed to complete this lab, we began with the known information. The mass of any object involved in the collision was found rather easily. The mass of each cart is given as 250 g as is each additional metal bar added to the cart. The initial velocity and final velocity were found using LoggerPro software, which creates measurements of velocity. Velocity is the rate of change of position, and when all position values are input-- velocity, and subsequently momentum, can be found. By analyzing an object's position in time against its mass, its amount of motion ca be found, both before and after the collision.

To calculate the momentum for both initial and final of the two carts, we took the mass of each given cart (separately) and multiplied it by velocity. We did this for both initial and final velocity. At this point, the initial and final momenta for the red and blue cart. At this point, the percent difference between these two values could be found, and total momentum for both initial and final velocity could be calculated.

IN EXAMPLE:

(Blue cart mass) x (blue cart's initial velocity)= blue cart's initial momentum __(Red cart mass)x (red cart's initial velocity) = red cart's initial momentum__
 * //__NOW ADD THESE TOGETHER TO GET THE TOTAL INITIAL MOMENTUM__//**

(Blue cart mass) x (blue cart's final velocity) =blue cart's final momentum (Red cart mass) x (red cart's final velocity) = red cart's final momentum
 * //__NOW ADD THESE TOGETHER TO GET THE TOTAL FINAL MOMENTUM__//**


 * Results**: The major result of our experiment was that we found that the law of conservation of mass was valid, exposing that the momentum was conserved.The purpose of the lab was to find out if the law of conservation applied to the two carts moving towards each other with different masses.

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 coefficient of static friction was determined to be 0.45. This was calculated from a measured angle using Newton's first law as described in the calculations.

1.) Momentum is a vector quantity (it has a direction associated with it). This is relevent for some collisions you analyzed. Which ones and why?
 * Lab Questions**:

This was relevent for Collision 7 Version 1 and Collision 9 Version 2 because both of the carts (not just the blue carts) had initial velocities- they both started moving towards eachother, effecting the directional path of travel.

media type="file" key="Collision 7 small.wmv" width="300" height="300"media type="file" key="Collision 9 small.wmv" width="300" height="300"

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? (For work see actual lab handout) C3V1: 3.5% C4V2: -16.14% C5V1: -19.36% C7V1: -207.5% C9V2: -6.77%
 * Collision 7 Version 1 was the collision with 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. -This is true because as long as it was a constant scale (i.e. using pixels) then all of the information would be portortioned (ratio-ed) the same.

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? -It would be better to use the velocity taken right before the collision happened. It would be more accurate because if we used the velocity taken right after we let go of the cart it would be going to fast and would have too much force.


 * Conclusion**:

We believe that the experiment produced a valid result supporting our statement which was that the law of conservation of momentum is true for carts colliding along one dimension; that the momentum would be conserved. All of our percent errors were small proving our statement was accurate. One reason why our experimental results differ from any accepted result is because there could have been human error. It was not the same EXACT force pushing the cart no matter how hard you tried, it would not be the same every time. We could measure how much force we put on the cart by using the stopper device we used before. Therefore we could adequately adapt the force, so that it is the same amount of force every time.

__**EXTENSION:**__ C3V1:elastic collision C4V2: elastic collision C5V1: could be elastic collision C7V1: inelastic collision C9V2: inelastic collision
 * See Chart above for Initial and Final Kinetic Energy Values.

1.) The way that we could tell that they would be inelastic is if the two carts group or couple together; then it is inelastic.

2.) Please see extension handout for work representation on these problems: C3V1.) 6.71% C4V2.) -171.405% C5V1.) -184.96% C7V1.) -20684.72% C9V2.) 72%

3.) We can tell if a collision will be inelastic, because if it is inelastic the two carts will couple together due to the velcro or magnets.

//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.//