Laws of Motion
© examsnet.com
Question : 32
Total: 40
A block of mass 25 kg is raised by a 50 kg man in two different ways as shown in 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?
Solution:
Here, mass of block, m = 25 k g
Mass of man,M = 50 k g
Force applied to lift the block,
F = m g = 25 × 10 = 250 N .
Weight of man,W = M g = 50 × 10 = 500 N
(a) When block is raised by man as shown in figure (a), force is applied by the man in the upward direction.
Action on the floor by the man= W – F = 500 + 250 = 750 N
(b) When block is raised by man as shown in figure (b), force is applied by the man in the downward direction.
Action on the floor by the man= W – F = 500 – 250 = 250 N
As the floor yields to a normal force of 700 N, the mode (b) has to adopted by the man to lift the block.
Mass of man,
Force applied to lift the block,
Weight of man,
(a) When block is raised by man as shown in figure (a), force is applied by the man in the upward direction.
Action on the floor by the man
(b) When block is raised by man as shown in figure (b), force is applied by the man in the downward direction.
Action on the floor by the man
As the floor yields to a normal force of 700 N, the mode (b) has to adopted by the man to lift the block.
© examsnet.com
Go to Question: