Velocity-time graph of a particle of mass (2 kg) moving in a straight line is as shown in Fig. 9.20. Find the word done by all the forces acting on the particle. 
.
A. `400 J`
B. `-400 J`
C. `-200 J`
D. `200 J`
.A. `400 J`
B. `-400 J`
C. `-200 J`
D. `200 J`
.
Correct Answer – C
Initial velocity of the partical : `v_(1) = 2 m//s`
Final velocity of the partical . `v_(f) = 0`
From work energy theorm
`W_(“net”) = Delta K.E = K_(f) – K_(i)`
`(1)/(2) m (v_(f)^(2) – v_(i)^(2)) = (1)/(2) (2) (0 – 400) = – 400 J`