Question

A proton in a uniform electric field moves along a straight line with constant acceleration starting from rest. If it attains a velocity $4\times {10}^3$ $km/s$ at a distance of $2cm$, the time required to reach the given velocity is :

Answer 1

$v^2=u^2+2as$
$u=0,s=2\times {10}^{-2}mt$
$a=\frac{v^2}{2s}=\frac{(4\times {10}^3\times {10}^3{)}^2}{2\times 2\times {10}^{-2}}m/s^2$

$a=4\times {10}^{14}$