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Linear Motion-Definition, Example, and Types

August 2, 2022
written by Adeel Abbas

The motion of a body in line is called linear motion. Everybody moving in a straight line is in linear motion.

We live in the universe of repetitive motion. Such as:

  • Motion of sun
  • The motion of electrons around the atomic nucleus
  • The motion of a car

Every physical process involves motion so it is reasonable to discuss the study of motion.

A body is said to be at rest with respect to an observer if its position doesn’t change with the passage of time.

A body is said to be in motion if it changes its position with time with respect to the observer. Motion and rest are two relative quantities.

There are two types of motion

What Is Linear Motion?

Linear motion is nothing but the movement of an object parallel to the direction of its length. The motion of objects like the movement of a train is considered the linear motion, but when a train moves perpendicular to the direction of its length, and then it is considered a circular motion.

image showing the linear motion

When the Body moves with linear motion covers some distance which is called displacement. hence we can say that a car moving in straight direction is example of linear motion. The rate of change of displacement of the body moving with linear motion is called velocity or linear velocity.

Newton’s law of motion also applies to the body moving with linear motion.

The body having mass and velocity and moving in line with the product of mass and linear velocity is called momentum. Law of conservation momentum state that before and after collision momentum remains constant.

The motion of a train in circular motion is similar to the motion of a ball or a tennis racket. It moves in a complete circle. The motion of a ball in the opposite direction is considered rotational motion.

Types of Linear Motion

The four major types of simple linear motion are.

1. Uniform Linear Motion

 Uniform linear motion occurs when an object moves in a straight line at a constant speed. In this type of motion, the object covers equal distances in equal intervals of time. There is no acceleration or deceleration during uniform linear motion.


  • Speed remains constant throughout the motion.
  • Direction of motion remains unchanged.
  • Acceleration is zero, meaning there is no change in velocity over time.


  • A train moving along a straight track at a constant speed.
  • A person walking in a straight line at a consistent pace
  • A car cruising along a highway with the cruise control set.

2. Uniformly Accelerated Linear Motion

Uniformly accelerated linear motion happens when an object moves in a straight line and experiences a constant acceleration. This means that the object’s velocity increases or decreases by the same amount in each unit of time.


  • Velocity changes at a constant rate over time.
  • Acceleration remains constant throughout the motion.
  • Direction of motion may remain constant or change depending on the direction of acceleration.


  • An apple falling freely towards the ground under the influence of gravity.
  • A car accelerating from rest at a traffic light.
  • A rocket launching into space, gradually gaining speed due to propulsion.

3. Non-Uniform Linear Motion

Non-uniform linear motion occurs when an object moves in a straight line, but its velocity changes irregularly over time. This type of motion can involve varying speeds or changes in direction.


  • Velocity changes irregularly over time.
  • Acceleration may vary throughout the motion.
  • Direction of motion may change or remain constant, depending on external forces acting on the object.


  • A roller coaster descending down a track, speeding up and slowing down at different sections.
  • A pendulum swinging back and forth, with its velocity changing as it moves.
  • A ball thrown upwards, slowing down as it reaches its maximum height before falling back down.

4. Free fall motion

Free fall motion refers to the movement of an object under the influence of gravity alone, without any other forces acting upon it. During free fall, objects accelerate towards the Earth at a constant rate, resulting in a predictable downward trajectory.


  • Acceleration remains constant at about 9.8 m/s² due to gravity.
  • Direction of motion is always downward.
  • Velocity increases steadily with time.


  1. Dropping a pen from a desk.
  2. A skydiver descending towards the ground.
  3. A leaf falling from a tree.

Read Difference Between Linear Motion and Rotational Motion

Linear Motion Example

We mostly think that a car is moving in a circular motion because of the rotation of tires, but actually, the motion of a car is known as a linear motion.

Rocket propulsion and Projectile motion are also linear motions.

The motion of an automobile is considered a form of linear motion. When a train travels in a straight line, it is considered as a straight motion. Similarly, the motion of a bus is considered a straight motion because it has a set of wheels.

An airplane is considered a flying machine, and when it is flying, it is considered as a motion in the air. When an airplane is flying toward the sky, it is considered as a motion in the downward direction, but when an airplane is flying downwards, it is considered a motion in the upward direction.