The definition of acceleration
Acceleration is the rate of change of velocity as a function of time.
For example a car traveling at 50 km/hr starts to accelerate, 10 seconds after, its speed changes to 100 km/hr then the acceleration of the car during the time can be calculated as below:
initial speed = 50 km/hr
final speed = 100 km/hr
the change of speed = 100 - 50 = 50km/hr
time = 10 seconds = 1/360 hr
thus the acceleration = (50km/hr) / (1/360 hr) = 18000 km/ hour2 = 1.38 m/ s2
the formula I am using here is: a = (v2 - v1)/t
where,
a: acceleration
v1: initial speed
v2: final speed
t: time