If the velocity of an object changes from 15 m/s during a time interval of 4s what is the acceleration of the object

The acceleration of an object is defined as change in velocity divided by change in time, that is,
Acceleration = change in velocity / change in time
In the question given above, 
Change in velocity = 15
Change in time = 4
Acceleration = 15 /4 = 3.75
Therefore, acceleration = 3.8 m/s^2.

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