The Office Chair and Conservation of Momentum

On this grand ole two day sojourn from school due to the snow, said snow was quite heavy and wet so when I finished shoveling I had no desire to create a blog post. On Thursday, I collected a few robotics team members and had them sit in some of Mr. Irwin's office chairs. I had one of them, Nate, place his feet on the back of Jacob's chair and while both are stationary, he would push off from Jacob's chair giving them an initial velocity in opposite direction. With the two students in office chairs and a meter stick on the desk, I called out to them to push off which propelled both chairs away from each other, transferring Nate's initial energy into momentum for both of them before they slow to a stop.

After inserting the video into Logger Pro, I then analyzed the two office chairs and the velocities of Nate's chair and Jacob's chair throughout the collision. The graphs below is the data from this analysis. The values for the velocity are not actually negative but the result of the motion of the the two chairs in the video.

Graph of Nate's Chair

Graph of Jacob's Chair

Using the values obtained by analyzing the graph and by collecting data on the weights of the two chairs with the people in them, I was able to use these values in solving the equations of momentum and energy in determining what type of collision was depicted in the picture. After doing the math, its is clear that the collision was inelastic as momentum was not conserved.

During the inelastic collision, a total of approximately 17.47 Joules of energy was lost after the collision.This loss could be attributed to many different factors including mistakes made during analysis and filming of this blog post, but the biggest influences were outside any issues. The rollers on the office chairs still had friction with the floor causing them to slow down over time. In addition, the uneven floor of Mr. Irwin's room may have had a negative effect. The movement of the roller chair's also may have been affected by Jacob dragging his feet on the ground briefly during the video, which was not discovered until analyzing the data. Aside from these major factors, there were many other outside effects and data inaccuracies that caused the collision to be inelastic losing energy and momentum instead of conserving the momentum.

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