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Homework Help: Accounting For Error on Air Track, Conservation Lab

  1. Oct 15, 2012 #1
    This is a conservation of momentum/energy lab. We have an air track with motion sensors at both ends. Bumpers are staged to give elastic collisions. There are two gliders on the track. For this part the second glider remains stationary near the center of the track. The first glider is sent to collide with the second. The motion sensors track their positions and give us the information I provided below. To give us an accurate graph we had to fix much larger flags to the gliders which increase air resistance. From this we have to prove that momentum and energy are conserved.

    Now here is the catcher. My professor told us we have to be under 0.1% error.

    How I've been calculating this out is by taking the velocity right before the collision and both right after on the graph and using that to find kinetic energy. That by itself on this particular run gives me a little under 3% error. Now because the collision is not instantaneous there is a dt. So I found the work done by air resistance over the uninterrupted part of the graph. Assuming this remained constant through the collision (I'm guessing this is where I'm wrong) I applied that dW/dt to the collision time, meaning I accounted for the work done by air resistance. No mater at what points I find the work or try to manipulate these numbers I cannot get a value below even 1%. Best I can come up with is about 1.3% error.

    Now what can I do to account for this error. If there is 3% error I need to account for those nonconservative forces.

    Also, this is my first college physics class so I don't have anything to compare to. Doesn't 0.1% error sound kind of extreme?

    Glider 1 (blue) 0.2007g
    Glider 2 (red) 0.1901g

  2. jcsd
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