Purpose: Look at a two-dimensional collision and determine if momentum and energy are conserved.
Model: P0=Pf and P=mv, 1/2m1v0^2=1/2m1v1^2+1/2m2v2^2
P is the momentum, P0 is the initial momentum, Pf is the final momentum, m is the mass of the object, and v is the velcity of the object.
Process: We weigh the mass of the glass ball and the steel ball, Mg=0.0196kg and Ms=0.069kg. First, we level the the glass the table and place a telephone on the top of the table. We gently set the stationary glass ball on that level table, and we use another glass ball to aim the stationary glass ball so that it could hit the side of the stationary ball. We start the slow motion camera to record, and we push the ball to hit the stationary ball. Then, we use the glass ball as the stationary ball, but we use a steel ball to be the rolling ball.
After recording these two vedio, we upload these vedio from the telephone to the computer. We use the software Quick to edit the vedio. Then, we open the vedio by using the Logger Pro. We change the frame rate to 240fps. We add the point on the vedio to mark the motion of the balls.
Then, we add the new column about the momentum of rolling ball in x-axis and y-axis and the momentum of stationary ball in x-axis and y-axis by using P=mv.
As the graph show, in two different experiment, the total momentum of two balls is constant in x-axis and y-axis. The total momentum does not change during the collision. The power of the entire system should not be change during the elastic collision. However, the power in the entire system is not constant, and it decrease a little bit when the balls hit each other; therefore, we can know that this collision is not an elastic collision. There are some power changing to other energy form.
We use the Logger Pro to find out the center of mass of entire system. Then, we figure out that the motion of center of mass is a straight line, and the momentum of the center of mass is constant.
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