## Demonstrations

The importance of this component is to clarify some of the physics that the students have gone over. By seeing some of the physics at work, they'll get a better understanding of how some of these principals work.

Unfortunately, the equipment I used when giving my demonstrations is quite expensive. If you aren't able to acquire equipment similar to that which I used, I hope that my demonstrations will at least give you some ideas for possible demonstrations.

I used a VSCOPE system which tracks the position of 4 buttons. The VSCOPE is then able to feed out graphs for position, velocity, and acceleration into my computer. I used the buttons from the VSCOPE on 2 collision carts which traveled on a near frictionless 2.2 m track (the carts and the track are from PASCO).

First I set out to prove Newton's Third Law. One of the carts I used had a plunger(spring triggered). I placed the carts(of equal mass) in the middle of the track, set off the plunger between the carts, and showed how they exert an equal force on each other and therefore travel and equal distance. Next, I balanced the track(with the carts in the middle) on a block of wood. By setting off the plunger against the 2nd cart, the two carts set off in opposite directions and hence kept the track balanced(well, at least for a little bit). Then I added different masses to the carts and set off the plunger. This showed how there is an equal amount of work done.

The second principal I showed was the conservation of momentum. By using VSCOPE, I was able to show that momentum from before and after a collision is conserved(elastic or inelastic collision). This was easily done by using carts of equal mass, plotting the velocity graphs, and comparing the total velocity before and after collision.

Finally, by plotting an acceleration graph with VSCOPE, I showed what kind of acceleration these carts go through in a collision. An example of this is when I set off 2 carts against each other. They were both traveling about 0.5 m/s. The maximum acceleration at any 1/20 th of a second of the collision was 287 m/s^2 . I then made some aluminum car bodies( I did this by wrapping aluminum foil around a model car which was slightly larger than the carts) and then taping these aluminum bodies to the carts. When I put the carts through the same collision that I had previously done, the maximum acceleration at any 1/20 th of a second was 97 m/s^2. This purpose of this demonstrations was to show how a prolonged time of collision would result in a huge drop in force experienced by the vehicle. This would also demonstrate the significance of having a reasonable crumple zone in front of a vehicle.