Plan the investigation
What students will do
Start with a guided comparison, then plan an investigation, analyze a graph, and check a prediction.
- Compare launch speeds. Use the distance-to-center graph to distinguish nearly circular paths from paths whose radius changes.
- Design and collect. Choose at least five radii with central mass fixed. Adjust launch speed to find a nearly circular orbit at each radius.
- Linearize the results. Transform radius and speed data to form a straight line. Use the slope to determine the central mass.
- Explain and predict. Evaluate the radius–speed relationship, then predict and test a circular speed at an unused radius.
What students will learn
- Use radius measurements to judge whether an orbit is circular.
- Connect gravity with the inward acceleration required for an orbit.
- Infer central mass from a graph-based model.
Common misconception
Does doubling orbital radius halve circular speed?
Students test the relationship between speed squared and inverse radius.