# Spin the wheel and measure its angular acceleration

If you spin a wheel rapidly, then release it, it will gradually slow down and finally come to a halt. The question of the day is is the angular acceleration constant?

Here's how to answer the question.

1. Place a piece of masking tape on the rim of a wheel to serve as a marker
2. Rest one end of the axle on top of some pieces of paper on the tabletop. Have one person hold the axle vertical (so the wheel is horizontal) and spin the wheel as fast as he can.
3. Assign a second person with a stopwatch to measure the time it takes the wheel to rotate 3 times.
4. Make measurements every 10 seconds until the wheel stops spinning. You should have at least 8 measurements.
5. Make a neat table showing your measurements. Compute the angular speed for each measurement and add it to the table.
6. Estimate the uncertainty in your values of angular speed. Explain how you did it.
7. Make a graph which shows angular speed as a function of time since the wheel started spinning.

Using your table and your graph, you must answer as many of the following questions as you can before class ends.

1. Estimate the average angular acceleration during the first 20 seconds of the experiment. Be sure to include an uncertainty.
2. Estimate the average angular acceleration during the last 20 seconds of the experiment. Be sure to include an uncertainty.
3. Did the wheel decelerate at a constant rate? Explain.
4. What was the angular displacement of the wheel during the first 10 seconds of the experiment?
5. What was the angular displacement of the wheel during the last 10 seconds of the experiment?
6. Estimate the total angular displacement of the wheel from start to finish.
7. Pretend that during this experiment, the wheel had not been spinning horizontally, but was rolling down the hallway outside the classroom. Would it have reached the far end of the hallway before stopping?

Staple together all your work. Write the names of all group members on the first sheet. Place your work in the folder on your table.