Question

A body is projected from ground obliquely during downward motion power delivered by gravity to it

Answer 1

Power delivered by any force is given by

$P = \frac{dW}{dt}$

here W = work done by the force

here we can write

$W = F.s$

Now from above equation

$P = \frac{d{F.s)}{dt}$

so

$P = F.\frac{ds}{dt}$

$P = F.v$

now the power delivered by the force will be positive if the angle between applied force and velocity is acute angle or less than 90 degree'

so here when object is moving downwards

angle between gravitational force and velocity of the object will be less than 90 degree

so power delivered will be

$P = Fvcos\theta$

all terms are positive

so power delivered will be positive here