Three blocks of masses 3 kg, 6 kg and 1 kg are connected by a string passing over two smooth pulleys attached at the two ends of the horizontal surface. If the co-efficient of friction between the block and the surface is 0.6, the frictional force acting on the block of mass 6 kg is

Options

A. 36 N
B. 30 N
C. 20 N
D. 10 N

Explanation

`f_(s("max"))=muMg =0.6 xx 6xx10=36N`
`T_(1)=10N and T_(2)=30N`
Frictional force, `f=30-10=20N`
Since `20lt f_(s("max"))`
`therefore f_(s)=20N`