Question

Two balls at the same temperature collide. What is conserved?
A. momentum
B. Kinetic energy
C. velocity
D. temperature

Answer 1

Hint: We are given that, the temperature of two balls are the same then which of the following options will be conserved. To choose the correct option, apply elimination methods to eradicate the wrong options. When two balls of the same temperature meet, some of their KE is converted into other forms of energy, such as heat energy and second energy.

Complete step by step solution:
To know which of the options will be conserved, we’ll use the elimination method. Explain each option:
There will be impulsive force due to which velocities of both the balls will change. Also, kinetic energy is a scalar quantity. When the work done on the body by the force then the kinetic energy of the body increases (same amount) and when opposite force applied to the body then kinetic energy will be reduced.

The decrease in the body's kinetic energy is equal to the work done by the body against the retarding force. It implies that kinetic energy will not be conserved, and it will change. On the other hand, Momentum is known as vector quantity. Therefore, the momentum of two balls will be conserved. Temperature will not be conserved as there is a loss in kinetic energy which changes the temperature.

Hence, option A is the correct answer.

Note: The law of momentum conservation is one of the most powerful rules in physics. The law of momentum conservation is as follows. When two objects collide in an isolated system, the total momentum of both the objects before the collision equals the total momentum of the objects after the collision. That is, the momentum acquired by the second object equals the momentum lost by the first object.