Plan the investigation
What students will do
Start with a guided comparison, then plan an investigation, analyze a graph, and check a prediction.
- Compare top readings. Run several bottom starting speeds and measure speed and tension directly above the pivot.
- Design and collect. Choose at least five starting speeds while keeping string radius and mass fixed. Use the same top location each time.
- Analyze a linear graph. Transform the starting-speed data and fit the top-tension relationship. Interpret the slope and intercept.
- Explain and predict. Combine energy and the inward force balance to predict and test tension for an unused starting speed.
What students will learn
- Apply a radial force balance at the top of a circle.
- Connect bottom and top speeds with energy conservation.
- Interpret a fitted model’s mass dependence and force offset.
Common misconception
Must tension equal weight at the top?
Both forces contribute to the inward net force; their relationship also depends on speed and radius.