Question

The pulley arrangement of fig. are identical. The mass of the rope is negligible. In (a) mass m is lifted up by attaching a mass (2 m) to the other end of the rope. In (b), m is lifted up by pulling the other end of the rope with a constant downward force F = 2 mg. In which case, the acceleration of m is more ?

Answer 1

Case (a) :

Case (b) : FBD of mass m

ma′ = T – mg

ma′ = 2 mg – mg

⇒ ma′ = mg

a' = g

So in case (b) acceleration of m is more.