A block of mass 25 kg is raised by a 50 kg man in two different ways as shown in the figure. 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?
Answers
# Answer - (b) Lifting weight by pulley is preferable.
# Explaination-
# Given-
Mass of block m = 25 kg
Masa of man M = 50 kg
# Solution-
Force applied on the block,
F = 25 × 10 = 250 N
Weight of the man,
W = 50 × 10 = 500 N
(a) Directly lifting weight -
In this case, the man applies a force in the upward direction.
This increases his apparent weight.
Action on the floor by the man = F + W = 250 + 500 = 750 N
Here, action on the floor is more than normal force. 750 N > 700 N, thus the floor will yield.
(b) Using pulley to lift weight -
In this case, the man applies a force in the downward direction.
This decreases his apparent weight.
Action on the floor by the man = W - F = 500 – 250 = 250 N
Here, action on the floor is less than normal force. i.e. 250 N < 700 N, thus the floor will not yield.
Therefore, the man should adopt second method for lifting the block without floor yielding.
Hope this helps you...
Answer:
Explanation:
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 =
Force applied on the block, F = 25 x 10 = 250 N
Weight of the man, W = 50 x 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.