Question

In the case of uniform circular motion, which one of the following physical quantities does not remain constant?
A. mass
B. speed
C. linear momentum
D. kinetic energy

Answer 1

Hint: The momentum is defined as the product of mass and velocity. That means momentum depends on both mass as well as velocity. As velocity is a vector quantity which has both magnitude and direction. That is why momentum is also a vector quantity.

Complete step by step solution:
In uniform circular motion, the tangential acceleration is zero because of uniform motion. In this motion the magnitude of the velocity remains constant whereas its direction continuously changes. Therefore, the speed is constant throughout the motion. As we know the momentum is directly proportional to mass and the velocity.

As velocity is a vector quantity due to it having both magnitude and direction. So, in uniform circular motion the direction of the particle is always changing throughout the motion. Thus, velocity will also change in the circular motion. Therefore, the linear momentum will also be changing in uniform circular motion.

Hence option C is the correct answer.

Note: When any object is in motion it means the object must have momentum. For example, if a boy is riding a bicycle on the road with uniform motion, then the bicycle must have momentum. In physics, we calculate momentum as the product of mass and velocity as:
Momentum=mass\[ \times \] velocity
Or \[p = m \times v\]
As velocity is a vector quantity due to which momentum is also considered a vector quantity. This means momentum has a significance of magnitude and direction.