Three blocks of masses 5 kg, 3 kg and 2 kg are placed on a rough surface as shown in figure. Coefficient of friction between block and surface is same for all the blocks and is equal to `mu = 0.2` . A horizontal force of 15 N is applied on 5 kg block. The force exerted by 3 kg block on 2 kg block is : (g = 10 m/`s^(2)`)

Options

A. 15 N
B. 5 N
C. zero
D. None of these

Answer

C

Explanation

Let friction between 5 kg and surface be `f_(1)`, 3kg and surface be `f_(2)` , 2kg and surface be `f_(3)`. Then
`(f_(1))_("max") = (0.2 (50) = 10 N`, `(f_(2))_("max") = (0.2) (30) = 6N`
`(f_(3))_("max) = (0.2) (20) = 4N`
`(f_(1) + f_(2))` is sufficient to balance the external force. so normal between 3 kg and 2 kg is zero.