 × ## Introduction

The concept of motion is related to the change in the position of an object when measured from a fixed point of reference. You would be surprised to know that everything in this world is constantly moving, even if it appears stationary. This is because the Earth itself revolves around the sun. At the same time, there is also motion in this world you can see. Examples of this include vehicles, trains, airplanes, etc. In summer, your ceiling fan spins to propel air toward you, which is also a type of motion. And everything related to motion can be understood in terms of the velocity and acceleration of the object in question. Let us discuss the latter in detail.

## What is acceleration?

Acceleration is a vector quantity that measures the rate of change of velocity of an object with respect to time. That is, Suppose that an object was moving in a straight line and its velocity changed from u to v. If v exceeds u, it means the object must have sped up and the acceleration will turn out to be positive. It is also possible for the object to slow down, leading to a smaller v and thus, a negative value of acceleration. This is known as retardation. When there is no change in the velocity of the object, it is said to have zero acceleration.

When an object is moving randomly, its velocity changes at every instant, and its motion is termed acceleration motion. Sometimes, the amount by which the velocity changes each second remains constant, giving rise to a constant acceleration. The motion of this type is said to be uniformly accelerated. On the other hand, non-uniform acceleration leads to non-uniform changes in velocity.

## Unit and Dimensional Formula

The SI unit for acceleration is ms-2. This can be easily derived from its formula since velocity is measured in ms-1 and acceleration is velocity divided by time. Other units for acceleration include km h-2.

The measurement of physical quantities also involves a dimensional analysis, which specifies the basic physical quantities that can be used to specify it. For acceleration. The dimensional expression is [M0LT-2]

## Types of Acceleration

### 1. Average Acceleration

Over time, the value of acceleration may not remain constant at every interval. However, across the whole journey, the average value of the acceleration can be found by taking the difference in the final and initial velocities and dividing them by the time taken. That is,

### 2. Instantaneous Acceleration

The value of the acceleration of an object at a particular instant in time is known as instantaneous acceleration. It is obtained by taking the limiting case of the formula for acceleration. That is, ### 3. Centripetal acceleration

When an object tied to a string is whirled around, it moves in a circular path. In such a case, even though its speed does not change, the direction of its velocity changes at every instant in time and thus, an object in circular motion is in accelerated motion.

The acceleration responsible for keeping objects on a circular path acts towards the center of the circle and is known as centripetal acceleration. It is given by: 