Question

A particle moves with a velocity $(5i -3j + 6k) ms^{-1}$ undre the influence of a constant force $F=(10 i +10 j +20 K)N .$ The instantaneous power applied to the particle is

• A. $200\,Js^{-1}$
• B. $40\,Js^{-1}$
• C. $140\,Js^{-1}$
• D. $170\,Js^{-1}$

Answer 1

Answer: (C)

Velocity v = (5i - 3j + 6k) $ms^{-1}$
and force F = (10i + 10j + 20k ) N
hence Power P = F. v
$= (10i + 10j + 20k) (5i -3j + 6k)$
= 50-30+120
= 140 W = 140$ Js^{-1}$