Question

A body of mass 3 kg at rest is acted on by a force and the body moves through a distance 20 m in 5 s. Force on the body is

• A. 4.8 N
• B. 2.4 N
• C. 60 N
• D. 10 N

Answer 1

Answer: (A)

4.8 N

Answer 2

Here, $m = 3 \: kg,$
$u = 0, s = 20 \: m , t = 5s$
Using kinematic equation, $s = ut + \frac{1}{2} at^2$
$20 = 0 \times 5 + \frac{1}{2} \times a \times (5)^2$ or $40 = 25a$
or $a = \frac{40}{25} = \frac{8}{5} m \: s^{-2}$ .
$\therefore \, \, \, F = ma = 3 \times \frac{8}{5} = \frac{24}{5} = 4.8 \: N$