Q.
Velocity-time graph of a particle of mass 2 kg moving in a straight line is as shown in figure. Work done by all forces on the particle is
A) 400 J
B) $- 400\ J$
C) $- 200\ J$
D) 200 J
Explanation
(b) Initial velocity of particle, $v_{i} = 20\ ms^{- 1}$
Final velocity of the particle, $v_{f} = 0$
According to work-energy theorem,
$W_{net} = \mathrm{\Delta}KE = K_{f} - K_{i}$
$= \frac{1}{2}m(v_{f}^{2} - v_{i}^{2})$
$= \frac{1}{2} \times 2(0^{2} - 20^{2})$
$= - 400\ J$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.