In the shown system, the 2 kg block has acceleration 2 m s⁻² to the right. Find the spring extension and the acceleration of the 4 kg block at that instant. Take k = 1000 N m⁻¹, μ values as shown and g = 10 m s⁻².

Question

G1 Physics · Accepted Answer

Apply Newton's second law to the 2 kg block including the applied 20 N force, kinetic friction and spring force. This gives spring force 12 N, hence x = 12/1000 = 0.012 m. Using the same spring force and friction on the 4 kg block gives acceleration 2 m s⁻². Option A.