question_answer

The minimum force required to move a body of mass m vertically upward is

A)  mg                                        

B)  mg/2

C)  more than 2mg               

D)  more than mg

Correct Answer: D

Solution :

                Let us assume that body is moving upwards with acceleration a. The weight, \[w=mg\]of the body acts downward. At equilibrium, \[R=mg\]                 Now, when the body starts moving upward,. then we have                 \[R-mg=ma\] \[\Rightarrow \]               \[R=mg+ma\] This shows that an additional force \[(ma)\] is required to lift up the body. Hence, minimum force required is                 \[(mg+ma)>mg\]