If an object of mass 2 kg is thrown up from the ground reaches a height of 5 m and falls back to the Earth (neglect the air resistance). Calculate
Total work done by gravity both in upward and downward motion and mention the physical significance of the result.

Explanation

When the object goes up, the displacement points in the upward direction whereas the gravitational force acting on the object points in downward direction. Therefore, the angle between gravitational force and displacement of the object is `180^(@)`.
The total work done by gravity in the entire trip (upward and downward motion)
`W_("total")=W_(up)+W_(down)`
`" "=-100"joule"+100"joule"=0`
It implies that the gravity does not transfer any energy to the object. When the object is thrown upwards, the energy is transferred to the object by the external agency, which means that the object gains some energy. As soon as it comes back and hits the Earth, the energy gained by the object is transformed to the surface of the Earth (i.e., dissipated to the Earth).