Question

A ball is at rest at the top of a hill. It rolls down the hill. At the bottom of the hill the ball hits a wall and stops.
Which energy changes occur?
A) Gravitational potential energy, internal energy, kinetic energy
B) Gravitational potential energy, kinetic energy, internal energy
C) Kinetic energy, gravitational potential energy, internal energy
D) Kinetic energy, internal energy, gravitational potential energy

Answer 1

Hint:The energy stored in any object due to its height or position is known as gravitational potential energy. When an object is placed at height, it gets attracted towards Earth due to which the energy is stored. This energy is increased when two objects are made to interact with each other.

Complete step-by-step answer:
Step I:
When the ball is present at the top of the hill due to its height from the ground it has gravitational potential energy stored in it.
Step II:
When the ball starts moving and rolls down the hill, then its stored potential energy is converted into kinetic energy. It is this kinetic energy that is responsible for the motion of the objects.
Step III:
From the principle of conservation of energy, it is clear that the energy can never be created or destroyed, it is just converted from one form to another. If the balls suddenly stop while moving, it stops. The kinetic energy is then converted into thermal energy which is stored as internal energy.
Step IV:
Therefore the correct sequence is :
Gravitational potential energy, kinetic energy, internal energy

Option B is the right answer.

Note:It is to be noted that the thermal energy can also be evolved in the form of heat energy. Therefore, thermal energy is nothing but the change in the potential energy of the system. But internal energy is different from thermal energy. Thermal energy is the sum of net potential energy and the kinetic energy of the system.