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 \[(g=9.8\text{ }m{{s}^{-2}})\]

A)  0.015 N               

B)  0.15 N

C)  0.030 N               

D)  zero

Correct Answer: A

Solution :

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