A particle moves with a velocity 5i-3j+6k m/s under the influence of a constant force F= 10i+10j+20k . The instantaneous power applied to the particle is

Q:A particle moves with a velocity m/s under the influence of a constant force . The instantaneous power applied to the particle is:
(A) 200 J/s
(B) 40 J/s
(C) 140 J/s
(D) 170 J/s

Solution : P = F^→.v^→
= (10i + 10j + 20k ).(5i – 3j + 6k )
= 50 – 30 + 120
= 140 J/s