Average Speed

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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 =

d2 – d1

 

t2 – t1

 

 

 

 

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 = d2 – d1

= 6.6 - 0

=   6.6

= 3.3 m/s

 

* Time          t2 – t1

2-0

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 = d2 – d1

= 30 - 6

= 24

= 8 m/s

 

* Time          t2 – t1

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 = d2 – d1

= 62.9 – 27.2

= 35.7

= 35.7 cm/s

 

* Time          t2 – t1

7- 6

1

 

 

 

 

 

 

 

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