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.