Wednesday, July 1, 2015

Modeling Instruction in Physics: Acceleration Practicum

Today we had another lab practicum! This time, involving acceleration.

Our group's scenario this time was to release a buggy (traveling with constant velocity) at the same time as we released a ball on a ramp, so that the buggy would catch the ball at the bottom of the ramp. To make sure we didn't just time the ball and then time the car, Bryan told us he would decide how high up the ramp we'd be releasing the ball and would tell us right before it was time to start. We had to be ready to make a quick calculation of where the buggy had to start from in order to catch the ball. 

Once again, we divided into two groups: one to find the velocity of the car and one to find the acceleration of the ball on the ramp. Finding the velocity of the car was straight forward; we've done that plenty of times. But I was surprised to see the other half of our group timing to see how long it would take the ball to travel the full length of the ramp. That's how I'd find the average velocity, but that isn't useful at all. What they were doing, though, was quite smart. They were using a displacement equation we'd developed earlier which involved acceleration, and they were planning to plug in the displacement and the time to solve for it.

Once we had the acceleration of the ball and the velocity of the car, it was quite easy to write an equation for each. We even took the time to solve them for the variables we needed (time from the ball's equation and position from the car's equation).

Here's how we did:

So close! It hit the back of the car. If only we'd started the buggy 1 cm farther away...

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