Force and Motion

Force and buckling explorations

Force and buckling exploration. Distribute a cardboard and cardstock strip to each student. Students will find out about the different forces the strips sustain when pushing at different distances from a fixed pivot. They do this by pushing on an output link of their own mechanism with each of the strips. Here are the instructions:

1.

Finger experiment. Instead of using the pegboard input to your mechanism, you will use each of these strips as the input link. Here is how you will do this.

Select one of the outputs of your mechanism. You will first use your finger to push it, then the cardboard strip, then the cardstock strip.
Begin at the end of the output and push it with your finger.
Go 2” (4 holes) toward the fixed pivot and push the lever back and forth with your finger.
Go 2” more toward the fixed pivot and again push the lever back and forth with your finger.
Once more, go 2” more toward the fixed pivot and again push the lever back and forth with your finger.
Write in your Science notebooks about any changes in how much you had to push.

2.

Cardboard strip experiment. This experiment uses a cardboard strip instead of your finger.

Hold the cardboard strip at one end. Put the other end against the same output of your mechanism. Repeat the experiment you did with your finger.
Begin at the end of the output, push it with the cardboard strip.
Move the cardboard strip 2” closer to the fixed pivot and push the lever. Repeat this 2” closer to the fixed pivot.
Write what happens with how hard you have to push.

3.

Cardstock strip experiment. Now use a cardstock strip instead of your finger.

Hold the cardstock strip at one end. Put the other end against the same output of your mechanism. Repeat the experiment you did with your finger.
If the cardstock buckles, hold it closer to where you push on the output. How far is it from where you hold the cardstock strip to the output when it no longer buckles?
Keep holding the cardstock strip at the place it didn’t buckle. Use it to push the output at a point closer to the fixed pivot. Does it still resist buckling? If it buckles, hold it closer to where you push the output until it doesn’t buckle.
Once more, use the cardstock strip closer to the fixed pivot to push the output link. What do you observe?