A ring of mass 0.35 kg is threaded on a horizontal wire and moves at a uniform speed under a horizontal force of 2.4 N applied parallel to the wire. Taking $g=10\text{ ms}^{-2}$ , what is the coefficient of friction between the ring and the wire?

A0.34

B0.69

C1.46

D6.86

Explanation

At uniform speed the net force is zero, so friction balances the applied force:

F=2.4

N. The normal reaction equals the weight,

R=0.35\times10=3.5

N. So

\mu=F/R=2.4/3.5\approx0.69

Derived from ZIMSEC Maths Paper 1, November 2008, Q11 (Statistics)

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A ring of mass 0.35 kg is threaded on a horizontal wire and moves at a uniform speed under a horizontal force of 2.4 N applied parallel to the wire. Taking g=10 ms−2g=10\text{ ms}^{-2}g=10 ms−2, what is the coefficient of friction between the ring and the wire?

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A ring of mass 0.35 kg is threaded on a horizontal wire and moves at a uniform speed under a horizontal force of 2.4 N applied parallel to the wire. Taking $g=10\text{ ms}^{-2}$ , what is the coefficient of friction between the ring and the wire?