N3LFP: Block Slide Challenge

Block Slide Challenge

One of the aspects of my class that I, and the students, find most engaging are the challenges. These are often called physics practicums but I don't really like that word we just call them challenges.

We do challenges in all levels of physics that I teach. And I do them with the physics teachers with whom I work in the summers as well.

There is the T-Bone challenge where we try to get two constant velocity buggies to crash in the middle of the classroom.

There is the Police Chase challenge where a constant velocity buggy is chased and caught by a constant acceleration fan cart.

There is the Paper River challenge where they have to place a constant speed buggy onto a piece of paper that moves at a constant speed (it is about 3 meters wide) at some angle and it has to travel straight across and hit a target.

There is the Bombs Away challenge where students drop a sand filled balloon into a constant speed buggy from about 7 meters up.

There are lots of projectile motion challenges - from easy horizontal shoots to more complex up and down projectiles.

There is the Cup and Foil Challenge (formerly the egg challenge) where a heavy object hanging on a spring has to be dropped so that it will just touch the foil on a cup but not break through.

There is the Pendulum and Troll where they time the swinging of a pendulum to knock a troll out of a constant speed buggy.

This particular challenge happened in the AP class where they are currently studying work and energy. Ostensibly the question is this, given a block compressing a spring; how far will the block slide before coming to a stop?

At the lab station each group has track, a block and a rubber band set between two clamps. I told them that their task was to figure out how far back to pull the block against the spring so that it would slide down the track and come to rest with part of the block hanging off the edge.

I asked them what they thought they would need to know and they responded with: the mass of the block, the coefficient of friction between the block and the table and the spring constant of the rubber band.

Some groups decided to set a slide distance and the calculate the pull back distance of the rubber band. Other groups decided to set a pull back distance and then calculate the slide distance of the block.

Either way they chose, they were on their own. There are no directions for this. And they struggle! But they are supposed to. What I find most exciting is that they find it hard and persevere.

Here is the video of one of the groups who had first time success.