Question

A block of mass 25 kg is raised by a 50 kg man in two different ways as shown in the figure below. 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

Question :

A block of mass 25 kg is raised by a 50 kg man in two different ways as shown in the figure below. 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.​

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Answer :

Mass of the block = m = 25kg
Mass of the man = M = 50kg
Acceleration due to gravity = g = 10 m/s²

Therefore, Force applied on the block by gravity = F = 25 x 10 = 250N
Weight of the man = W = 50 x 10 = 500N

Answer 2

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750 N and 250 N in the respective cases; Method (b)

Mass of the block, m = 25 kg

Mass of the man, M = 50 kg

Acceleration due to gravity, g = 10 m/s2

Force applied on the block, F = 25 × 10 = 250 N

Weight of the man, W = 50 × 10 = 500 N

Case (a): When the man lifts the block directly

In this case, the man applies a force in the upward direction. This increases his apparent weight.

∴Action on the floor by the man = 250 + 500 = 750 N

Case (b): When the man lifts the block using a pulley

In this case, the man applies a force in the downward direction. This decreases his apparent weight.

∴Action on the floor by the man = 500 – 250 = 250 N

If the floor can yield to a normal force of 700 N, then the man should adopt the second method to easily lift the block by applying lesser force.

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