Two bodies of masses `m` and `4m` are attached to a light string as shown in figure. A body of mass m hanging from string is executing oscillations with angular amplitude `60^@`, while other body is at rest on a horizontal surface. The minimum coefficient of friction between mass `4m` and the horizontal surface is (here pulley is light and smooth)

Options

A. (a) `1/4`
B. (b) `3/4`
C. (c) `1/2`
D. (d) `1/8`

Answer

C

Explanation

Velocity at lowest position `=sqrt(2gl(1-cos60^@))=sqrt(gl)`
`T=mg+(mV^2)/(l)=mg+m/lgl=2mg`
`:. T=mu4mgimplies1/2`