Question

The mechanical energy of a freely falling body is:
A) Constant in all instants
B) Maximum in the beginning
C) Minimum in the beginning
D) Maximum in the middle

Answer 1

Hint: Mechanical energy is the sum of kinetic energy and potential energy of a system. It should be noted that during an elastic collision, the mechanical energy of the system remains conserved, but in an inelastic collision, some amount of the mechanical energy is converted into thermal energy.

Complete step by step answer:
Conservation of mechanical energy states that when an isolated system is acted upon by the conservative forces the sum of systems kinetic and potential energy remains constant.
Hence, when we apply the principle of conservation of mechanical energy, energy remains constant.
The mechanical energy of a free-falling body always remains to conserve during a free fall. For example, if you drop an object intentionally from your hand, you can observe that it will fall at a constant speed until it reaches the ground.
So, we can say that its mechanical energy is constant in all instances.

$\therefore $ The mechanical energy of a freely falling body is constant in all instants. Hence, option (A) is correct.

Additional information:
According to the principle of conservation of mechanical energy, when a body is subjected only to conservative forces then the mechanical energy of the body remains constant.
When a conservative force moves a body from one point to another then the work done by the conservative force does not depend upon the path traveled.
When a non-conservative force is applied on a body then, the work done by the non-conservative force depends on the path traveled.

Note:
It should be noted that in real-life situations non-conservative forces are present for example frictional force, due to which the conservation of mechanical energy does not take place.
A body is said to be in free fall if no other force except gravity is acting on it.