A particle of mass `100 g` is thrown vertically upwards with a speed of `5 m//s`. The work done by the force of gravity during the time the particle goes up is

Options

A. 1.25 J
B. 0.5 J
C. `-0.5 J`
D. `-1.25 J`

Answer

D

Explanation

Using work-energy theorem, `W_("total") = DeltaK` i.e., work done by gravity should be equal to change in the kinetic energy of the particle.
`W_("gravity") = K_("final") - K_("intial") , " "W_("gravity") = (0 - 1/2 xx ((100)/(1000)) (5)^(2)) = 1.25 J`
Work done by force of gravity = -125 J.