Understanding average speed can help make predictions and lead to other
calculations. For example, two snowmobiles, Otter Pop and White Fang,
travel at different average speeds from one place to another.
- If Otter Pop gets to the destination first, what can you
say about its average speed? (If you need to draw a sketch to
clarify your ideas, go ahead!)
Now Slider and Mangler are traveling at the same average speed, but they
are going to different places. Mangler takes longer to get to its
- What can you say about Mangler's trip compared to
Slider's? (Feel free to make a sketch if it will help you.)
Most people are familiar with speeds in a narrow range of human
experience. A good runner can run about 7 miles per hour. A sprinter may
reach about 20 miles per hour. A fast car can go about 200 miles per hour
on a racetrack only! :) An airplane averages about 450 miles per
hour. Very slow things and very fast things are harder to measure and
- What are the slowest and the fastest things you can
think of? (Name at least 2 for each.)
One question puzzled scientists for many years. That question was,
"How fast does light travel?" In 1638, Galileo, a famous
scientist, decided he wanted to try and find out.
- What two things are needed to find the speed of
an object? Are they the same things you would need to find the
speed of light?
Galileo used a lantern to generate a light and had an assistant located a
mile from him. At an exact predetermined time, Galileo uncovered the
lantern. The assistant noted the time, and a calculation was made. The
next night, they repeated the experiment, only this time, they used a
longer distance. But, even though the distance had changed, the time
remained the same. Their method didn't work.
- Why do you think their method for finding the speed of
light didn't work? How would you be able to fix their experiment
by using some of today's technology?
We now know the speed of light to be about 186,000 miles per second.
Miles per second! You can figure out
light's average miles per hour by multiplying 186,000 miles by 60 seconds
to get miles per minute (60 seconds in a minute), and then multiplying
your new number by 60 minutes to get miles per hour (60 minutes in an
- How far does light travel in an hour?
This astonishing value for the speed of light is recognized by scientists
to be the maximum speed that an object can travel. It is nature's speed
The speed equation (speed = distance/time) can be used to predict how long
a trip will take. If the speed and distance are known, the equation can
be used to solve for time instead of speed. You and your family are going
to travel to a great amusement park that is 650 miles away. You'll be
taking your family car, but your parents drive very slowly, only 50 miles
per hour. So, put your speed (50 miles per 1 hour) where the speed part of
the equation is, and your distance (650 miles) where the distance part of
the equation is. Since you don't know the time yet, put a t where
time will go. Your equation should look like this:
Now you just need to solve the problem.
- How long will it take you to get to the amusement park?
The next time you travel, find out how far you are going, how fast your
vehicle (car, plane, bus, train) will be traveling, and then figure out
how long it will take. See if you are right!