Advanced — Cue BallHardQuestion 30371
Question
A cue hits a billiard ball (radius R) at height h above the table. For pure rolling immediately after the hit, h must equal:
- AR/2
- B2R/3
- C7R/5Correct
- DR
Correct answer
7R/5
Explanation
Impulse at height h gives translational impulse J and angular impulse J(h−R) about centre. For pure rolling: v = ωR → J/m = (J(h−R)/I)×R. For solid sphere I = 2mR²/5: (h−R) = 2R/5 → h = 7R/5.