Introduction to Motion - Definition, Types, Examples, FAQs

What is Motion?

Motion definition: Motion is the change in the position of an object with respect to time and a reference point. If the position of a body changes compared to its surroundings, it is said to be in motion. For example, a moving car, a falling stone, or the Earth revolving around the Sun are all examples of motion.

Terms Related to Motion

As we have read above in the example of moving passenger and roadside trees, it is clear that motion also depends upon the condition of the observer whether he is stationary or moving.

The motion of an object is mainly described using the following terms:

1. Distance – Distance is defined as how far an object has moved on the ground. It is the main parameter which is used to describe the motion of an object. Distance represents the change in position of an object.
2. Displacement – Displacement is defined as the shortest distance traveled by an object. It also represents the change in the position of an object like distance.
3. Time – It is also a main act to define the motion of an object. The change in position of an object is measured with respect to time only.

Different Types of Motion With Examples

There are 4 main types of motion depending on how an object changes its position with respect to time.

Linear Motion

Linear motion is the type of motion in which an object moves in a straight line or along a curved path in the same direction. The position of the object changes with time, but the path followed is always linear (straight or curved).

Examples:

• A car moving on a straight road.
• A ball falling vertically from a height.
• A train moving on a straight track.

Types of Linear Motion:

1. Rectilinear Motion: Motion along a straight line (e.g., motion of a bullet).
2. Curvilinear Motion: Motion along a curved path (e.g., motion of a car on a curved road).

Oscillatory Motion

When an object is moving back and forth about its fixed mean position, then the object is said to exhibit oscillatory motion. Some of the common examples of oscillatory motion are as follows:

• In a pendulum clock, the pendulum moves back and forth about its mean position.
• In stringed musical instruments, the string moves back and forth about its mean position when it is touched.

Rotatory Motion

When an object rotates or moves in a circle on its fixed axis, then the object is said to exhibit rotatory or rotational motion. Some of the common examples of rotational motion are as follows:

• The motion of the Earth about its axis is a type of rotatory motion.
• The movement of the steering wheel while driving a car is also a type of rotatory motion.

Circular Motion

When an object is moving in a circular path or we can say along the circumference of a circle, then the object is said to exhibit circular motion. Some of the common examples of circular motion are as follows:

• All the planets revolving around the sun exhibit circular motion
• Merry go round ride is also a type of circular motion.

Applications of Motion

Everything in this universe exhibits motion and nothing is stationary, hence it is difficult to give all the examples of motion. But some common examples of motion are easily observable and understandable for all including:

1. Transportation: Motion is used in vehicles like cars, buses, trains, ships, and airplanes to move people and goods.

2. Sports: Motion is involved in running, cycling, swimming, and the movement of balls in games.

3. Engineering and Machines: The working of engines, turbines, and robots is based on the principles of motion.

4. Space Science: Motion explains the revolution of planets, the orbit of satellites, and the movement of rockets.

5. Daily Life: Walking, riding a bicycle, or even throwing an object are simple applications of motion.

Laws of Motion

The laws of motion are the fundamental principles which was formulated by Isaac Newton. The three laws are given below:

1. First Law of Motion: An object remains in a state of motion or at rest unless compelled by an external force.
   $F_{\text {net }}=0$ if velocity is constant (either at rest or constant speed in a straight line).
2. Second Law of Motion: The force exerted on a body is directly proportional to the rate of change of momentum.
   $F=\frac{d}{d t}(p)$
   OR
   The force acting on a body is equal to the product of the mass and acceleration of the body.
   $F=m a$
3. Third Law of Motion: Every action has an equal and opposite reaction.
   $F_{\text {action }}=-F_{\text {reaction }}$

Equations of Motion

The three equations of motion is given as follows:

The first equation of motion

$v=u+a t$

where,

• $v=$ Final velocity
• $u=$ Initial velocity
• $a=$ Acceleration
• $t=$ Time

The second equation of motion

$s=u t+\frac{1}{2} a t^2$

where,

• $s=$ Displacement (distance traveled)
• $u=$ Initial velocity
• $a=$ Acceleration
• $t=$ Time

The third equation of motion

$v^2=u^2+2 a s$

where,

• $v=$ Final velocity
• $u=$ Initial velocity
• $a=$ Acceleration
• $s=$ Displacement