Advanced — Vertical Circle FrictionHardQuestion 30670
Question
A ball moves in a vertical circle on a track with friction (μ). Work done by friction per revolution:
- A−2πμmgCorrect
- B−2πrμmg
- C−2πμmgr (circumference × friction force on normal)
- DDepends only on μ and height
Correct answer
−2πμmg
Explanation
For a ball on a circular track, the normal force varies with position. Work by friction per revolution = −∮μN ds, which requires integration. For a flat horizontal circle, W_friction = −μmg×2πr. For a vertical circle, the calculation is more complex.