The body moves with uniform acceleration and from the moment the start of the countdown in 1 minute changes

The body moves with uniform acceleration and from the moment the start of the countdown in 1 minute changes the speed from 9 km / h to 54 km / h to determine the speed of the body.

Let’s convert the time from minutes to seconds. Since there are 60 seconds in one minute, then t = 60s
Let’s convert the speed in m / s: V1 = 2.5m / s, V2 = 15m / s
Then a = (V2-V1) /t=12.5/60=0.21m/s^2