question_answer

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

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                      \[{{F}_{air}}=m(g-a)\]                                  \[=0.05(9.8-9.5)\]                                   \[=0.015\,\,N\]