Question

A man whose weight is 650 N, standing on the ground, raises a load of 3000 N by means of single string system of pulleys. There are six light pulleys in each block. The thrust of the man on the ground is 
1. 120 N
2. 135 N
3. 150 N
4. 175 N
5.

Answer 1

Correct Answer - Option 3 : 150 N

Explanation:

In a single string system of pulleys:

Velocity ratio = n

where n = number of strings between fixed pulley block and movable pulley block.

Considering 100% efficiency:

Mechanical advantage = Velocity ratio = n = 6

Mechanical advantage = \(\frac{Weight}{Tension}=6\)

Tension = Weight/6 = 3000/6 = 500 N

So, Thrust of man on ground = W - T

= (650 - 500) = 150 N