What is energy?

Energy is a fundamental thing necessary for the survival of life. Energy in physics is defined as the capacity to do work. As with many things in physics “work” has a very specific definition. Work is defined as a measure of energy transfer to move an object by a certain distance by imparting an external force in the direction of motion.

Based on this specific definition, interestingly a person who is standstill and holding a very heavy object is not doing any work because the object is not actually moving. But we all know that holding a heavy object is indeed difficult and we’ve to expend a lot of energy to keep holding it. We need to spend energy to counter the force of gravity to keep the object in place. But what work is being done? The work that is done here is actually in the cells in ours muscles. The cells are triggered to contract repeatedly to the keep the muscle in the holding position. In order to do this the body uses the stored chemical energy which in turn is obtained through the food we consume.

In summary energy occurs in nature in various forms which can in turn do various types of work.