Page 21 - Science Class 6 Times Publication

A body is said to be in motion if it changes its position with respect to
its surrounding.

A body is said to be at rest if it does not change its position with
respect to its surrounding.

Rest and motion are relative terms. A body can be in motion when
compared to one body and can be at rest at the same time when
compared to another body. For example, when you are traveling by
bus, you change your position as compared to outside road, trees,
buildings, etc. Therefore, you are in motion in such case. At the same
time, when you are compared with your fellow passengers, you are in
same position with respect to them. Therefore, you are in rest in such
case. Thus, you seem to be in both motion and rest states. It depends
upon comparison. Therefore, rest and motion are relative terms.
Types of motion

There are various types of motion. Some of them are discussed below:

1) Linear motion 6) Spiral motion
2) Circular motion 7) Vibratory motion
3) Rotatory motion 8) Curvilinear motion

4) Oscillatory motion
5) Random motion

Linear motion (Translatory motion)

When a body moves in a straight line in a particular direction,
its motion is called linear motion. It is also known as translatory
motion. For example, motion of vehicles in a straight road, motion of
aeroplane, motion of stone released from a catapult, a stone dropped
from a height, etc. Gravity also produces translatory motion.

Linear motion of a car

Times' Crucial Science and Environment 17 Book 6