Answer : His acceleration from 5 s to 10 s will be, 

Solution : Given,
Initial velocity = 3 m/s
Final velocity = 7 m/s
Initial time = 5 s
Final time = 10 s
Acceleration : Acceleration is defined as the rate of change of velocity with respect to the time taken.
Formula used :

where,
a = acceleration
 = change in velocity
 = change in velocity
 = change in time
 = change in time
Now we have to calculate the acceleration from 5 s to 10 s :
Put all the given values in the above formula, we get


Therefore, his acceleration from 5 s to 10 s will be, 
