Average Acceleration
Acceleration = a change in speed: (Speeding up…Slowing
down… or changing direction) 
Average
acceleration is the rate at which velocity changes. Average acceleration is
the change in velocity divided by an elapsed time. For instance, if the
velocity of a marble increases from 0 to 60 cm/s in 3 seconds, its average
acceleration would be 20 cm/s/s. This means that the marble’s velocity will
increase by 20 cm/s every second. See the table below: 
Time (Seconds) 
Velocity (cm/s) 
0 
0 
1 
20 
2 
40 
2 
60 
4 
80 
Here is the formula we will use: 
Average
Acceleration = Velocity Time 
= “change
in” or “difference of”
Here is another way of looking
at the formula: 
Average Acceleration = 
_{} Velocity = v_{2} – v_{1} _{} Time
t_{2} – t_{1} 
Sample
problem)
At 12:00, a rocket begins to accelerate from 20 mph. At 12:05 the rocket is
traveling at 280 mph. What is the acceleration of the rocket? 
Average Velocity = 
_{} Distance = d_{2} – d_{1} 
= 280  20 
= 260 
= 52 mph/min 

_{} Time t_{2} – t_{1} 
5 0 
5 
