A particle of mass `100 g ` is thrown verically upward with a speed of `5 m//s` . The work done by the 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") = Delta K`
i.e., woek done by gravity should be equal to change in the kinetic energy of the particle.
`W_("gravity") = (k_(f"inal") - K_("initial"))`
`W_("gravity") = (0 - (1)/(2) xx ((100)/(1000))(5)^(2)) = - 1.25 J`
Work done by force of gravity `= - 1.25 J`.