Question

Which of the following is not in uniform motion?
A) A bullet travelling with constant speed in straight line
B) A swinging pendulum
C) The earth rotating about its axis
D) Both B & C

Answer 1

Hint: Uniform motion is the type of motion which travels in the straight line and covers the equal distance in equal intervals of time. Analyze all the conditions given in the question and see in which condition the object has constant speed.

Complete step by step answer:
Uniform motion can be defined as the type of motion which travels in the straight line and covers the equal distance in equal intervals of time. In this type of motion, the velocity remains the same during the whole journey. If a body is involved in rectilinear motion and the motion is consistent, then the acceleration of the body must be zero. It is just opposite of non – uniform motion which covers unequal distance in equal intervals of time. The speed of the object is different during the whole journey of the object.

As we have to find which condition does not follow the uniform motion, we can also say that we have to find which condition follows the non – uniform motion. So, the four conditions are –
1) The bullet has a constant speed and travels in a straight line, so it will have a constant velocity and hence it is in uniform motion.
2) Swinging pendulum is under the action of gravitational force and is also changing its direction - hence it is not in uniform motion. It is non – uniform motion.
3) The rotation of the earth in non – accelerated motion and hence it is a uniform motion.
Hence, the correct option is (B).

Note: The earth moves with same speed around its axis and covers equal distance in equal intervals of time and the swinging pendulum can also become slow after some time so, it is the non – uniform motion.