Answer:
When it's speed or velocity changes with time
Step-by-step explanation:
In simple terms, acceleration means the change in the velocity at which object moves in accordance to the time interval at which then velocity change occurs. This means that for acceleration to have taken place, there has to be a difference in travel or moving velocity of the object with a certs in time interva.the proportion of velocity change and time is the value acceleration.
Hence, for body which maintains a contain rate of velocity, that is (no net increase or decrease in the velocity over a measured time interval, then th acceleration of such body is ZERO.
ACCELERATION = (Final - Initial Velocity) / time interval. Acceleration is measured in m/s²