Laws of Motion

Question : 5 of 40

Marks: +1, -0

A constant retarding force of 50 N is applied to a body of mass 20 kg moving initially with a speed of 15 m s

^{-1}

. How long does the body take to stop?

Solution:

Here,

M = 20\ \mathrm{kg};

F = -50\ \mathrm{N}

(retarding force)

Now,

F = M a

\therefore\ a = \frac{F}{M}

= \frac{-50}{20} = -2.5\ \mathrm{ms}^{-2}

Also,

v = u + a t

Here,

u = 15\ \mathrm{m}\ \mathrm{s}^{-1};\ v = 0

\therefore\ 0 = 15 + (-2.5) t

t = 6\ \mathrm{s}

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