What quantity did you change?
Labs / Physics
Ball on a String
A ball whirls in a circle because the string keeps pulling it inward — that inward pull is the centripetal force, F = mv²/r. Change the speed, radius, and mass, then cut the string and watch the ball shoot off along the tangent, not outward.
Labs / Physics / Ball on a String
Ball on a String
A ball whirls in a circle because the string keeps pulling it inward — that inward pull is the centripetal force, F = mv²/r. Change the speed, radius, and mass, then cut the string and watch the ball shoot off along the tangent, not outward.
Why it matters
Why explore this?
Physics explains how changes in forces, energy, motion, and matter produce results we can measure. This model lets you test one part of that relationship at a time.
Explore
Try the model
Fc 9.0 NTension 9.0 NPeriod 1.57 s
Investigate
Questions to test
Predict first, try it in the model, then use what you observe to answer.
What to try
- When you cut the string, does the ball fly straight outward or off to the side? Why that direction?
- Double the speed. Does the required force double, or grow faster than that?
- Widen the radius while keeping the speed fixed — does the string need more tension or less?
- If you were swinging a real bucket, would a heavier ball be harder to keep in the circle?
- What combination of speed and radius gives the shortest period — the fastest lap around the circle?
Explain
Make sense of what happened
Name the quantity you changed, the quantity that responded, and the physical rule connecting them. Use a readout or visible change as evidence.
Check
Before you leave
What measurable result changed?
Which physical idea connects them?
If you can answer all three using evidence from the model, you understand the main idea. If not, return to Explore and change one setting at a time.