# Rest and Motion in physics explanation with examples

Learning objectives

## Concept of Rest and Motion

In our daily life ,we see lots of things moving around. For example car passing through from one place to other, person riding on a bicycle and many more like this.
Apart from moving things and objects we also observe things that are not moving at all.

So you have two states of objects in physics. Rest and motion are these two states of objects under consideration.

## What is motion in physics?

In scientific terms let us now state motion definition physics

an object is said to be in state of motion, if it changes its position with the description of time.

This is how we define motion in physics.

## What is rest in physics ?

In scientific terms definition of rest in physics is

If an object does not change it position with the passage of time then it is at rest

## Rest and motion examples

### Examples of motion in physics

Some examples of motion in physics include

• moving car
• rotating ferris wheal
• person walking on the street
• ballerina dancing
• blood flowing in veins and arteries

This short video is showing some examples of motion or moving people/objects

### Example of rest in physics

Some examples of objects at rest in physics are

• book kept on table
• benches in the park
• person sitting on the chair

apart from these many more examples of rest and motion can be found in nature or space around you.

## Both the motion and rest are relative terms

Let us explain above statement with the help of example.

Let us consider a mobile on the table is resting at its position.

(a) is it at rest or

(b) is it moving i.e., changing its position with the passage of time.

Now we have stated before that Motion and rest are relative terms

☛   So for a person sitting on a chair near the table mobile is at rest.

☛   Now consider a hypothetical scenario where we station our self on moon.

☛  Now from there earth seems to change its position with time. This is because earth is rotating on its axis. So mobile along with the table is changing its position.

☛   So, it is moving for a person tracking it from moon.

Simplest case of motion is rectilinear motion. It is the motion of the object in a straight line or one dimension. But this is not the only kind of motion we study in physics.

We study about rotational motion. In this type of motion objects rotate about a certain fixed axis of rotation.

There are few other types of motions for example circular motion, periodic motion, simple harmonic motion etc.

## What are point objects in kinematics?

In our description of object in motion, we sometimes treat the moving object as an point object. So this is an expression for objects in used in kinematics

### Point object physics definition

Object under consideration can be treated as point object if the size of the object is much smaller than the distance traveled by it in a reasonable time duration.

### Point object examples

• Length of a motor car traveling a distance of 500 km can be neglected w.r.t distance traveled by it. So, motor car is treated as point object in calculations.
• Earth or other planetary objects can be considered as a point object for studying their motion around the Sun. Even Sun can be treated as point object if we started talking in terms of Galaxies or inter galactic distances.
• A cricket ball dropped from a height of 200 m can be considered as point object

Here in kinematics, we study ways to describe the motion without going into the cause of the motion.