Work Done against the Force - QS Study

Work done against the force

A person has lifted a bag of rice on his head from the ground. Again, a book has been lifted in the bookshelf from the floor or a table. In these two cases, work is done against the gravitational force. So, if a body is moved against the point of action of the applied force i.e., the point of action of the force moves against the direction of the force, then it is understood that work is done against the force. In this case work done against the force is negative work.

Example and explanation: Climbing stairs and lifting objects is work in both the scientific and everyday sense—it is work done against the gravitational force. When there is work, there is a transformation of energy. Work done by a body is against the applied force if the displacement is in a direction opposite to the force. In the case of gravity, if a body is lifted above the ground, work is done against gravity.

All bodies with mass are attracted towards the earth by gravity, so when a body is lifted one has to do work to raise it.

Work done against gravity = Force x Displacement = Weight x Height = mgh = gravitational potential energy stored in the body.