A person brings a mass of `1 kg` from infinty to a point `A`. Initially, the mass was at rest but it moves at a speed of `3 m//s` as it reaches `A`. The work done by the person on the mass is `- 5.5 J`. The gravitational potential at `A` is

Options

A. `- 1 J//kg`
B. `- 4.5 J//kg`
C. `- 5.5 J//kg`
D. `- 10 J//kg`

Answer

D

Explanation

`W = DeltaE = E_(A) - E_(a)`
`= (K_(A) + U_(A)) - (K_(a) + U_(a))`
`= (K_(A) + mV_(A)) - (0 + 0)`
`:. - 5.5 = (1)/(2) xx 1 xx (3)^(2) + (1) V_(A)`