Sign of Acceleration

In the previous segment, we learned how to calculate acceleration of a body. In this segment, we will learn about the concept of Negative acceleration.

Table of Contents

• Negative Acceleration
• Summary
• Did You Know?
• What’s Next?

 

What is Negative acceleration?

Acceleration is defined as the rate of change of velocity.

Acceleration and velocity are vector quantities and the direction of a vector quantity is defined with respect to a reference system.

Since, vector quantities can be positive or negative, acceleration of a body can also be positive or negative. The negative sign implies that the acceleration of the body is in the negative direction with respect to our reference system.

Let’s consider the x-y axis as our reference system, where the right hand side of the origin represents the positive direction and the left hand side of the origin represents the negative direction.

Representation of acceleration on X-Y axis

A body whose velocity is changing with time can either slow down or speed up . In both the cases, a body can undergo negative acceleration.

Case 1: Body slowing down in positive direction of our reference frame

Consider a body moving from point A to B in time(t) = 5 seconds, such that its initial velocity

(u) is 10 ? and the final velocity (v) is ^?.

? ?

Body slowing down

We can calculate the acceleration (a) of this body by the formula:

? = ?−?

?

? ?

Hence, ? = 4 ? −10 ?

2?

? = −3 ?

?2

This means that the body is moving with negative acceleration or its acceleration is in the negative direction with respect to our reference system.

Case 2: Body speeding up in the negative direction of our reference frame