Question

7. A boy of mass 40 kg stands in a frame of
mass 360 kg. He pulls on a light rope which
passes over a pulley. The other end of the
rope is firmly attached to the frame. What
force should be exerted by the boy on the
rope for the system to be in equilibrium?
(a) 40g
(b) 400g
(c) 200g
(d) 100g​

Answer 1

Answer: 200g

Explanation: As the boy stands in the frame the total mass = 40+360 = 400

Now, the total tension should balance the mg force ; but both the tensions are in the frame therefore

Total tension = 2T

So, 2T=(360+40)g

T=400g/2

T=200g N

Answer 2

The correct answer is option (c) 200g.

Given,

A boy of mass 40 kg stands in a frame of mass 360 kg. He pulls on a light rope that passes over a pulley. The other end of the rope is firmly attached to the frame.

To Find,

The force exerted by the boy on the rope for the system to be in equilibrium.

Solution,

Let us assume that the tension force in the string is T and R is the reaction force.

Now, the FBD of the boy will be

40g = R+T

T = 40g-R

The FBD of the block

T = 360g+R

On adding both the equation

2T = 400g

T = 200g

Hence, the boy should exert 200g force on the rope.

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