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

_{} Time 
20 
2 







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 – 27.2 
= 35.7 
= 35.7
cm/s 

_{} Time t_{2} – t_{1} 
7 6 
1 





