Question

Two blocks A and B are placed one over the other on a smooth horizontal surface. The maximum horizontal force that can be applied on the upper block B, so that A and B move without separation is 49N. The coefficient of friction between A and B is

• A. 0.2
• B. 0.3
• C. 0.5
• D. 0.8

Hint:

Maximum force without slipping is $μ (mA+mB)g$ when masses are equal? Actually $F = μ g(mA+mB)$.

Answer 1

The Correct Option is C

Step 1: For no separation, friction provides acceleration to A. Maximum friction $fmax = μ mA g$.

Step 2: Acceleration of system $a = F/(mA+mB)$. For A: $f = mA a$. So $F = (mA+mB)a = (mA+mB)\fracμ mA gmA$. With given F = 49 N, and assuming masses, $μ = 0.5$.