Read Vertical Circles: Separate Energy from Contact
Completing a vertical circle requires two ideas: energy tells you how speed changes, while tension tells you whether the string stays taut.
Motion and force questions become simpler when direction, starting condition, time and the acting forces are marked first.
Start with the condition
Use conservation of energy from the launch point to that top point.
Build the governing relation
Check the limiting tension at the top, not only at the bottom; that is where a slack string first fails the circular path.
Finish with a physical check
Check the limiting case before selecting an option: remove the special feature in the diagram or make the relevant parameter very large or very small. The result should reduce to a familiar relation.
OlympIQ exam lens
- ✓State the physical condition before choosing a formula.
- ✓Keep direction, sign and constraint information explicit.
- ✓Test one limiting case before committing to an option.
Setting the top speed to zero is insufficient—the string would go slack before the ball completes the circle.
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