A constant retarding force of 50 N is applied to a body of mass 10 kg moving initially with a speed of 10 $m{s}^{-1}$. The body comes to rest after

Here, F = -50 N (-ve sign for retardation)

        M = 10 kg, u = 10 $m{s}^{-1}$,   v = 0

As      F = ma

          a = $\frac{F}{m}$ = $\frac{-50 N}{10 kg}$ = -5 ${\mathrm{ms}}^{-2}$

Using v = u + at

           t = $\frac{v-u}{a}$ = $\frac{0-10 m{s}^{-1}}{-5 m{s}^{-2}}$ = 2 s