Question

A body of mass 10 kg is moving with velocity 4 $m{s}^{-1}$. The kinetic energy and momentum of the body is:

• A. 200 J and 160 kg $m{s}^{-1}$
• B. 400 J and 40 kg $m{s}^{-1}$
• C. 80 J and 40 kg$m{s}^{-1}$
• D. 80 J and 160 kg$m{s}^{-1}$

Answer 1

The correct option is C

80 J and 40 kg$m{s}^{-1}$

Given, mass of the body $m=10kg$ and velocity $v=4m{s}^{-1}$
Kinetic energy (K.E.) = $\frac{1}{2}m{v}^2$
$\Rightarrow$K.E. = $\frac{1}{2}\times 10\times$ $4^2$ = 80 J
Momentum (P) = mv
$\Rightarrow$P = 10 $\times$ 4 = 40 kg$m{s}^{-1}$
$\therefore$ Kinetic energy = $80J$ and momentum = $40kgm{s}^{-1}$