Motion in a Straight Line

What Is Motion in a Straight Line?

If an object changes its position with respect to its surroundings with time, then it is called in motion. It is a change in the position of an object over time. Motion in a straight line is nothing but linear motion. As the name suggests, it’s in a particular straight line, thus it can be said that it uses only one dimension.

Types of Linear Motion

The linear motion, also called the Rectilinear Motion can be of two types:

  1. Uniform linear motion with constant velocity or zero acceleration
  2. Non-Uniform linear motion with variable velocity or non-zero acceleration

Linear motion is the most straightforward kind of one-dimensional motion. As Newton’s first law of motion suggests, an object will either be at rest or continue to move in a straight line with a uniform velocity unless and until an external force is applied to it.

You are suggested not to confuse linear motion with general motion. As we discussed, linear motion is a one-dimensional motion. Still, in general, the motion has magnitude and direction both, i.e. an object’s position and velocity are described in vector quantities.

Read More: Vector and Scalar Quantities

Uniform Motion in a Straight Line

If a body travels in a straight line and covers an equal amount of distance in an equal interval of time, it is said to have uniform motion. In simple words, a body is said to have uniform acceleration if the rate of change of its velocity remains constant.

Motion in a Straight Line

The ball covers equal distance in equal intervals of time


If a car travels at a speed of 60 km/hour, it will cover a 1 km/minute. In this sense, the motion of car acceleration is uniform.

Watch the video and learn about motion in one dimension

Non-uniform Motion in a Straight Line

Unlike the uniform acceleration, the body is said to have a non-uniform motion when the velocity of a body changes by unequal amounts in equal intervals of time—the rate of change of its velocity changes at different points of time during its movement.


A boy is kicking a football. It might cover 4 meters in the first attempt, 6 meters in the second change, 9 meters in the third attempt and so on as per the velocity exerted by the boy.

The below video provides the Top 10 NTSE Important Questions on Motion Class 9

Motion in a Straight Line Formulas

Following are the formulas of motion in a straight line:

v =u + at
\(\begin{array}{l}s=ut+\frac{1}{2}at^{2}\end{array} \)
v2 = u2 + 2as

You may want to check out the following related videos for better understanding of motion and its characteristics.


Motion in One Dimension (1D)

If you wish to learn more physics concepts with the help of interactive video lessons, download BYJU’S – The Learning App.

Test your Knowledge on motion in a straight line


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  1. Nice app