Question

How long will it take a force of 20 N to stop a body of 5 kg which is travelling at 20 m/s?

• A. 10 s
• B. 20 s
• C. 5 s
• D. 15 s

Answer 1

The correct option is C 5 s

Given : $F=20$ N $m=5$ kg $u=20$ m/s $v=0$ m/s

Retardation of the body $a=-\frac{F}{m}=\frac{-20}{5}=-4$ $m/s^2$

Using $v=u+at$

$\therefore$ $0=20-4t$ $⟹t=5$ s