Question

Choose the incorrect option for a freely falling body in vacuum.

• A. When a freely falling body eventually stops on reaching ground, its kinetic energy becomes zero
• B. When a freely falling body eventually stops on reaching the ground, its kinetic energy is maximum just before reaching the ground
• C. Mechanical energy remains constant
• D.
  Kinetic energy + potential energy = variable

Answer 1

The correct option is C Mechanical energy remains constant

When a body falls freely, its initial velocity, u is 0. If it takes time t to reach the ground, its maximum velocity v becomes $\frac{1}{2}g{t}^2$ (just before hitting the ground).

Since no other force, except gravity, acts on the body, the mechanical energy of the freely falling body remains constant.
Kinetic energy + Potential energy = Constant
Hence, the correct answer is option (d).