A block P of mass m is on a frictionless horizontal surface. Another block Q of the same mass is kept on P and connected to a wall by a spring of spring constant k. μₛ is the coefficient of friction between P and Q. The blocks move together in SHM of amplitude A. The maximum friction force between P and Q is:

Question

G1 Physics · Accepted Answer

The two blocks move together, so total oscillating mass is 2m and ω²=k/(2m). The top block requires friction f=mω²x. Its maximum magnitude is at x=A: fₘₐₓ=m[k/(2m)]A=kA/2. Correct answer: B.