Plan the investigation
What students will do
Start with a guided comparison, then plan an investigation, analyze a graph, and check a prediction.
- Compare pulley masses. Measure acceleration and both rope tensions for several pulley masses with the hanging masses unchanged.
- Design and collect. Choose at least five pulley masses. Keep pulley radius and hanging masses fixed and measure during free motion.
- Linearize the data. Transform the acceleration relationship and fit a straight line. Use the model to infer gravitational acceleration.
- Explain and predict. Explain the torque supplied by unequal tensions, then predict and test acceleration for an unused pulley mass.
What students will learn
- Explain why a rotating massive pulley can have unequal rope tensions.
- Connect translational acceleration with rotational inertia.
- Use a transformed graph to test a coupled-system model.
Common misconception
Must tension be equal on both sides of one string?
A massive pulley requires a net torque to accelerate, which changes the tension balance.