A stone of mass 0.5 kg is whirled in a horizontal circle of radius 1 m at constant angular speed 4 rad s⁻¹ by a string. The tension in the string is:
A2 N
B4 N
C8 N
D16 N
Answer & Solution
Correct answer: C. 8 N
1. For uniform circular motion the only horizontal force is the tension, providing the centripetal force.
2. Centripetal acceleration = ω² r = 4² × 1 = 16 m s⁻².
3. T = m ω² r = 0.5 × 16 = 8 N.
4. Wrong picks come from forgetting to square ω (gives 2 N) or doubling (16 N).
_Source: NCERT Class 11 Physics Ch 4 "Laws of Motion", §4.10 Circular Motion, p. 62_
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