When you lift a box from the floor and put it on almirah, potential energy of the box increases but there is no change in its kinetic energy. If there is no change in its kinetic energy, then how does the potential energy increase?
When you lift a box from the floor and put it on the almirah, there is no change in its kinetic energy but the potential energy of the box increases.
Because work is being done on the box to put it on the almirah and this work will get stored in the box as its potential energy. So the potential energy of the box will increase.
During the lifting of the box, at every point, the external force is applied to the box in the upward direction and gravitational force is acting on the box in the downward direction.
These two forces are equal and opposite.
Therefore, there is no velocity change. As a result, the kinetic energy of the box will not change.