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

Explanation

In 1st case , man applies an upward force of 25 kg wt.r ( same as the weight of the block ) . According to Newtons's third law of motion, there will be a downaward reaction on the floor.
The action on the floor by the man , = 50 kg wt + 25 kg wt = 75 kg wt = 75 kg `xx 10 ms^(-2)` = 750 N
In case II , the man applies a downaward force of 25 kg wt. According to Newton's third law, the reaction is in the upward direction.
In this case, action on the floor by the man
= 50 kg wt - 25 kg wt = 25 kg wt = `25 kg xx 10 ms^(-2)` = 250 N
Therefore, the men should adopt the second method.