Q. At a certain instant, a body of mass 0.4 kg has a velocity of $\left( 8\widehat{\mathbf{i}} + 6\widehat{\mathbf{j}} \right)ms^{- 1}$. The kinetic energy of the body is
A) 10 J
B) 40 J
C) 20 J
D) None of these
Explanation
(c) $v = \sqrt{(8)^{2} + (6)^{2}} = 10ms^{- 1}$
$KE\ = \frac{1}{2}mv^{2}$
$= \frac{1}{2} \times 0.4 \times 10 \times 10 = 20$ J
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.