Question

What is mechanical energy ?

Answer 1

Mechanical energy is the energy possessed by an object due to its position and motion of the object. It can be either conservative or non-conservative.Energy is a scalar quantity it only has a magnitude. For potential energy the value of potential energy depends on the position of the particle which is a vector quantity and the value of kinetic energy depends on the velocity of the particle which is again a vector quantity.

Complete answer:
Energy can be either conservative or non-conservative. The principle of conservation of mechanical energy states that if a body or system is subjected only to conservative forces, the mechanical energy of that body or system remains constant. A field is said to be conservative if the work done in a cyclic path is zero and it is said to be non conservative if the work done in a cyclic path is greater than zero.

For a field to be non-conservative there must be a dissipative force present. In the real world for an object in one dimensional motion on a surface this dissipative force is friction, for an object falling in the action of gravity air drag or friction is the dissipative force. Both the motions are conservative if there are no frictions or dissipations.

We know that the mechanical energy possessed by any object depends on its mechanics that is on its position and momentum. So, mechanical energy of an object is the sum of its kinetic energy and potential energy, which depends on its momentum and position respectively.

So, Mechanical energy of an object is the sum of its kinetic energy and potential energy.

Note: Mechanical energy of an object does not depend on the internal structure of the object; it only depends on its momentum and position. Conservation of mechanical energy states that the mechanical energy of an isolated system remains constant in time, as long as the system is free of friction and other non-conservative forces.