In fig., a person wants to rise a block lying on the ground to a height h. In both the cases, if the time required is same, then in which case he has to exert more force? Assuem pulleys and strigns light.

Options

A. (i)
B. (ii)
C. same in both
D. cannot be determined

Answer

A

Explanation

Since `h=1/2 at^(2)rArr` a should be same in both cases, becauses h and t are same in both cases as given,

In (i) `F_(1)-mg=ma`
`rArr F_(1)=mg+ma`
In (ii) `2F_(2)-mg=marArr F_(g) =(mg+ma)/2 :. F_(1) gt F_(2)`