Question

Which of the following is not an example of uniform motion?
A.)A train going along the track in a steady speed
B.)Earth moving round the sun in a uniform motion
C.)A bus on its way to the market
D.)A vibrating spring in a sewing machine

Answer 1

Hint: A body is said to be in uniform motion if it traverses equal distances in equal intervals of time.

Complete step by step answer:
Let us consider each given case specifically.
When a train is moving along the track at a steady speed, it has a constant speed. Meaning it traverses an equal distance in an equal interval of time. Although it may change its direction which changes its velocity, its speed remains constant. Hence, it is a uniform motion.
The same applies for the earth moving round the sun. Considering it to be in a circular orbit, the direction changes at every instant, but given it stays in its own orbit, the speed remains constant. It feels an acceleration radially towards the centre. However, that being perpendicular to the direction of motion doesn’t affect the speed. Hence, it performs a uniform motion

A bus on its way to the market goes through various traffic conditions. Thus, its speed varies. At times it may stop. It changes direction. As such, its motion is completely non-uniform.
A vibrating spring in a sewing machine oscillates about a mean position. While running, and assuming there is no damping, the spring oscillates at a constant frequency. Although its direction is changing regularly, the distance traversed by it at a given interval remains the same. Hence, it is uniform motion.

Therefore, the correct option is C.

Note:
When looking for uniform motion, look for regularity, repetitiveness and constants of the motion. Certain aspects of the motion may vary, such as direction but still, the motion may remain uniform, as in case of circular and oscillatory motion.