Paper 1 · circular motion

A particle moves in a horizontal circle at a constant speed. If the mass is halved, the angular speed doubled and the radius unchanged, what happens to the centripetal force?

Adoubled

Bhalved

Creduced by a quarter

Dremains the same

Explanation: Centripetal force

F = m\omega^2 r

. Halving mass gives factor 1/2, doubling angular speed gives factor

2^2 = 4

. Net factor =

\frac{1}{2}\times 4 = 2

, so force is doubled.

ZIMSEC Physics Paper 1, June 2003, Q6

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