Question

Block A of mass 35 kg is resting on a frictionless floor. Another block B of mass 7 kg is resting on it as shown in figure. The coefficient of friction between the blocks is 0.5 while kinetic friction is 0.4. If a force of 100 N is applied to block B, the acceleration of the block A will be : (g = 10 m s^–2)

• A. 0.8 m s^–2
• B. 2.4 m s^–2
• C. 0.4 m s^–2
• D. 4.4 m s^–2

Answer 1

Answer: (A)

0.8 m s^–2

Answer 2

 7 kg body will slide because

F = 100 N >> limiting friction

 Friction b/w bodies is kinetic

f_k = _k mg = 0.4 × 7 × 10 = 28N

 a = 28/35 = 0.8 m/s²