Background:
Average Speed is the distance traveled divided by an elapsed time. For
instance, if you travel 100 miles in 2 hours, your average speed would be 50
miles/hour. Here is the formula we will use: 
Average Speed = Distance Time 
= “change
in” or “difference of”
Here is another way of looking at the formula:
Average Speed = 
d_{2} – d_{1} 

t_{2} – t_{1} 
1) A rock is dropped
from a cliff and it takes 2 seconds for the rock to fall 6.6 meters. What is
the rock’s average speed? 
Average Speed = 
_{} Distance 
= 6.6 m – 0 m 
= 6.6 m 
= 3.3
m/s 

_{} Time 
2 sec – 0 sec 
2 sec 






2) A boy rolls down a hill
on a skateboard. At time = 4 seconds, the boy has rolled 6 meters from the
top of the hill. At time = 7 seconds, the boy has rolled to a distance of 30
meters. What is his average speed? See the table below: 
Time
(Seconds) 
Distance
Rolled (Meters) 
4
seconds 
6 meters 
7
seconds 
30
meters 
Average Speed = 
_{} Distance = d_{2} –
d_{1} 
= 30  6 
= 24 
= 8 m/s 

_{} Time t_{2} –
t_{1} 
7 4 
3 






3) Analyze the
following table of data of an accelerating car and calculate the speed for
the two adjacent intervals. 
Time (seconds) 
Distance (cm) 
Speed (cm/s) 
6 
27.2 

7 
62.9 
? 
Average Speed = 
_{} Distance = d_{2} –
d_{1} 
= 62.9 cm –
27.2 cm 
= 35.7 cm 
= 35.7 cm/s 

_{} Time t_{2} –
t_{1} 
7 sec – 6 sec 
1 sec 



