Physics - NLM Question with Solution | TestHub
A constant horizontal force F = mg/2 starts acting on the block of mass m from the position shown. The spring is undeformed in the position shown and has a natural length L, while the blocks are initially stationary. The spring constant is k. The floor is frictionless. The mass of the hanging block is m/4, while the pulley is massless and frictionless. Assume that the block never leaves contact with the surface.

What is the initial acceleration of the block of mass ?
Options:
Answer:
Solution:
Initially the spring is undeformed, so it exerts no force. For block m: F - T = ma. For the hanging block m/4 (which rises as m moves toward F): T - (m/4)g = (m/4)a. Adding: mg/2 - mg/4 = (5m/4) a, so a = g/5. Answer: (A).
