An object of mass 2 kg falls from a height of 5 m to the ground. What is the work done by the gravitational force on the object? (Neglect air resistance, Take `g = 10 ms^(-2)`).

Explanation

In this case the force acting on the object is downward gravitational force `mvecg` This is a constant force Work done by gravitational force is
`W=underset(r_(i))overset(r_(f))intvecFdvecr`
`W=(Fcostheta)underset(r_i)overset(r_f)intdr=(mgcostheta)(r_(f)-r_(i))`
The object also moves downward which is in the direction of gravitational force `(vecF= mvecg)` as shown in figure. Hence, the angle between them is `theta=0^(@) cos 0^(@) = 1` and the displacement, `r_(f)-r_(i)=5m`
`w=mg(r^(f))-r_(i)`
`w=2xx10xx5=100J`
The work done by the gravitational force on the object is positive