Question

A body starts with velocity $u$ and moves in a straight line with constant acceleration $a$. When its velocity has increased to $5u$, the acceleration is reversed in direction, the magnitude remains the same. Find the velocity with which the body passes the starting point again.

Answer 1

$s_1=\frac{(5u{)}^2-u^2}{2a}=\frac{24u^2}{2a}$

$s_2=\frac{(5u{)}^2}{2a}=\frac{25u^2}{2a}$

$s=s_1+s_2=\frac{49u^2}{2a},u=0,v$

using$v^2-u^2=2as$

$v=7u$