Question

Can K.E. of a system be increased or decreased without applying any external force on the system?

Answer 1

Definition of kinetic energy

The energy possessed by a body due to its motion is termed kinetic energy. It is given as,

$KE=\frac{1}{2}m{v}^2$

where, $m$ is mass and $v$ is velocity.

Explaining the increase in kinetic energy:

1. When two oppositely charged particles are brought near each other, they will be attracted due to the force of attraction.
2. As the particles will get attracted towards each other, their velocity will increase.
3. Since kinetic energy is directly proportional to velocity, an increase in velocity will result in an increase in kinetic energy.

Explaining the decrease in kinetic energy:

1. When a ball bounces back from the ground to the air, the force of gravitation acts on the ball.
2. Due to the force of gravitation and the height acquired by the ball, the potential energy of the ball increases.
3. Since the ball slows down under the force of gravitation, and also, due to the increase in potential energy, kinetic energy decreases.

Yes, K.E. of a system can be increased or decreased without applying any external force to the system.