2025 · Q4
When a stone tied to a string is whirled in a circle, the work done on it by the string:
General KnowledgePhysics
- Ais positive.
- Bis negative.
- Cis zero.
- Ddepends on the mass of the stone.
Explanation
The tension in the string acts radially inward as the centripetal force, always perpendicular to the stone's instantaneous (tangential) velocity. Work done equals Fd cos θ, and since θ = 90°, cos θ = 0, so the work done is zero. The string changes only the direction of the stone's velocity, never its speed, so no energy is transferred regardless of the stone's mass.