Question

When is the acceleration taken as negative?

Answer 1

Acceleration

1. Acceleration can be defined as the rate of change of velocity with respect to time.

$a=\frac{v_2-v_1}{t}$

Here, $a$ is the acceleration, $v_2$ is the final velocity, $v_1$ is the initial velocity, and $t$ is the time.

2. Hence, when the final velocity of a moving body is more than the initial velocity, the value of the acceleration is positive.

3. It will happen if the direction of the acceleration will be the same as that of the moving body.

Negative acceleration

1. If the direction of the acceleration and the direction of the moving body are opposite to each other, the acceleration will be negative.
2. Negative acceleration is often referred to by the name retardation.
3. When a body is thrown upwards, the body loses its speed with respect to time.

It is due to the acceleration of the body acting downwards, while the body is moving upwards.

In this case, the acceleration is negative in nature, but the magnitude is the same as the acceleration due to gravity.