# The linear momentum p of a moving body varies with time according to equation $p=a+bt^2$ where a,b are constants. Net force acting on the body is

a) Constant

b) proportional to $t^2$

c) Inversely proportional to t

d) proportional to t

$F=\large\frac{dp}{dt}=\frac{d}{dt}$$(a+bt^2)$
$F=2bt$
$f \;\alpha\; t$
Net force acting on the body is proportional to t
Hence d is the correct answer.

edited Jan 26, 2014 by meena.p