A 2 kg block is kept on 1 kg block as shown. The friction between 1 kg block and fixed surface is absent and the coefficient of friction between 2 kg block and 1 kg block is μ = 0.1 . A constant horiz

Question

A 2 kg block is kept on 1 kg block as shown. The friction between 1 kg block and fixed surface is absent and the coefficient of friction between 2 kg block and 1 kg block is $μ = 0.1$ . A constant horizontal force $F = 4 N$ is applied on 1 kg block. If the work done by the friction on 1 kg block in 2s is - XJ, then find the value of X.

diagram

TestHub · Accepted Answer

Limiting friction f = 0.1 × 2 × 10 = 2 N ; the blocks slip (together would need 2.67 N). On the 1 kg block: a = ( 4 − 2 ) /1 = 2 m / s 2 , moving s = 2 1 ​ × 2 × 2 2 = 4 m in 2 s. W f ​ = − 2 × 4 = − 8 J , so X = 8.

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JEE Advanced 2028 (Class 11)