Question

A block of mass 25 kg is raised by a 50 kg man in two different ways, as shown in picture. What is the action on the floor by the man in the two cases? If the floor yields to a
normal force of 700 N, which mode should the man adopt to lift the block without the floor yielding ?
​

Answer 1

Answer:

• Mass of the block = 25 kg

• Mass of the man = 50 kg

• Acceleration due to gravity = 10m/s²

• 750N and 250N in the respective cases

• Force applied F = m×g = 25 × 10 = 250N

• Weight of the man = M g = 50 × 10 = 500N

Case (a) :-

The man applies a force in the upward direction. This increases his apparent

weight while he lifts the block directly.

Action = Force applied + weight of the man

$\implies\:\:250N + 500N$

$\implies\:\:750N$

Case (b) :-

The man applies a force in the downward direction. This decreases his apparent

weight while he lifts the block using a pulley.

Action = Weight of the man - Force applied

$\implies\:\:500-250$

$\implies\:\:250N$

The man should adopt the second

method if the floor can yield to a normal force of 750 N. Through this method he can easily lift the block by applying lesser force.

Answer 2

I hope you will understand with the help of this diagram