Question

define acceleration and give its SI unit .when is acceleration of a body is negative ?give two example of situation in which acceleration of the body is negative

Answer 1

The rate of change of velocity with respect to time is called acceleration.
It is unit less physical quantity.
1. When the velocity of body goes on decreasing.

Answer 2

1. The rate of change of velocity is called Acceleration.
2. The SI unit of Acceleration is m/s².
3. When the velocity of  a body decreases, the acceleration is in the opposite     direction of velocity and hence acceleration is said to be negative acceleration.