Two blocks of 2 kg and 4 kg are in contact as shown. The coefficient of friction between them is μ = 1/2. Forces F₁ = 2 N and F₂ = 20 N act in opposite directions. Find the friction force between the blocks.

Question

G1 Physics · Accepted Answer

If the blocks move together, their common acceleration is (2-20)/(2+4)=-3 m s⁻². For the 2 kg block, 2+f = 2(-3), so f = -8 N; magnitude 8 N. Limiting friction is μN = 10 N, so 8 N is feasible. Hence A.