Question

Why the acceleration is negative?

Answer 1

Acceleration:

The rate of change of velocity with respect to time is known as acceleration.

Explanation:

1. Acceleration, $a=\frac{∆v}{∆t}$, where $∆v$ is the change in velocity and $∆t$ is the time elapsed.
2. $∆t$ is always positive, whereas $∆v$ can be both positive and negative.
3. $∆v$ is positive when the magnitude of velocity increases.
4. $∆v$ is negative when the magnitude of velocity decreases.
5. $a$ will be negative when $∆v$ is negative.

Thus, acceleration will be negative when the body's velocity is decreasing with time.