Consider a particle on which constant forces ` F _1 = hati +2 hatj + 3hatk ` N and ` F_2 = 4 hati - 5 hatj - 2 hatk ` act together resulting in a displacement from position `r_1 = 20 hati + 15 hatj ` cm ` to ` r_2 = 7 hatk ` cm . the total work done on the particle is

Options

A. -0.48J
B. +0.48J
C. -4.8J
D. +4.8j

Answer

A

Explanation

Answer(1) Displacement of particle, `vecr = 7hatk - (20hati + 15hatj`)
= `7hatk - 20hati - 15 hatj` .
total work done = total force, displacement = `(vecF_1+ vecF_2).vecr` .
= `([hati + 2hatj +3hatk] + [4hati - 5hatj - 2hatk]). (7hatk - 20hati - 15hatj)`.
= [`5hati - 3hatj + hatk][-20hati - 15hatj+7hatk`].
= -48N-cm = -0.48joules