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Momentum and Kinetic Energy in 1-Dimensional Sticking Collisions

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We're going to be looking at collisions where the objects stick together during the collision. Now I'll demonstrate the collisions and get some data and later you'll use that data to determine whether momentum and kinetic energy are conserved in these collisions. We're using the same setup as in the past,  a low friction track, the track has been leveled so that the gliders don't have a tendency to drift one way or another, they move along it with fairly low friction, but they will slow down a little bit, so it's not completely frictionless, on each glider, there's a post-it note taped there, and the purpose of the post-it note is to trigger the photo gate timers as it passes through and that's how we measure the velocities of the cart. And you have noticed, it's a little difficult to pull these apart, the reason they stick is because there is Velcro on the front of them. There is a piece of Velcro on each side, and the opposite kind on each other side, so they will stick. So, for each collision, one cart will be stationary to begin with. I'm going to sit it right here, right before this photo gate, and the other cart to the outside of the other photo gate. The reason I chose to position like this, is almost immediately after the collision occurs, this post it note passes through the photo gate, so if there is any slowing down due to friction, it will be minimal. This will minimize the error due to friction. And for the same reason, this photo gate is close to this cart. So this should minimize the error due to friction and we should get better data.

So I will begin by positioning both of the carts in front of the photo gates, and give this a push. And let's see what the photo gates read. This one is 0.158 seconds, and this one is 0.077seconds.

Alright, now what I am going to do is put mass on these carts, and get some more data. So ill take one of these bars, and each bar is half of a kilogram, and each of these carts are 0.500 kg. So, that makes this car one full kg, and this one is still a half. Get this one ready, reset the photo gates, and go.

And the time readings are on this one 0.110 seconds, and on this one 0.070 seconds.

Alright lest change the bar to the other cart. Reset the gates. Now, that one you can see slowed down quite a bit, so there might be a significant influence of friction that we may have to watch for

And the time readings are on this one 0239 seconds, and on this one is 0.071 seconds.

You may have noticed that the second flag goes through the photo gate too. This flag went through first, followed by this one, and why doesn't this give us an incorrect reading. The reason is the timer stops after the first flag goes through.

Okay, I am going to put another bar on this cart, and move this bar to this cart. So now this cart is 1.500 kg, and the other cart is 0.500 kg. So this cart is 3x the other cart. Alright reset.

The time readings are 0.109 seconds and 0.078 seconds.

Let's do one more collision.

Take my last bar and put it on this one. So we got 1kg here, and 1.500 kg here. Reset.

And the times are 0.159 seconds and 0.087 seconds.

So with the data that you have, the times of each collision, and the width of the flag, which by the way is 5.00 cm or .0500 cm, and the cart masses, you will be able to determine if the energy of the carts is conserved or not.

 



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