question_answer

A body of mass 0.05 kg is observed to fall with an acceleration of\[9.5\text{ }m{{s}^{-2}}\]. The opposing force of air on the body is \[\left( g=9.8\text{ }m{{s}^{-2}} \right)\]

A)  0.015 N         

B)  0.15 N

C)  0.030 N          

D)  zero

Correct Answer: A

Solution :

From, Newtons laws of motion, \[mg-{{F}_{air}}=ma\] or \[{{F}_{air}}=m(g-a)\] \[=0.05(9.8-9.5)\] \[=0.015N\]