1. Speed measures how fast position changes

2. Speed Speed is how fast positions change with time distance Speed =
00:00
00:02
distance

3. Speed
A measure of how fast something moves through a particular distance over a definite time period.

4. You try
Suppose a race is 50 m and it takes an athlete 15 seconds to run it. Is that enough information to calculate the runner’s speed?
Think-pair-share (2 minutes)
YES, the formula for speed = distance
time

5. THIS IS YOUR AVERAGE SPEED
Imagine taking a road trip with your friends or family. When you travel in your car do you stay at a constant speed?
THIS IS YOUR AVERAGE SPEED

6. Average speed Usually objects do not travel at a constant speed.
Do you run at a constant pace when you run for a mile in PE class?
Think about when you are riding somewhere and you hit traffic.
It is more useful to calculate an objects average speed using the following equation:

7. Average speed example
Think about when you meet your friends at the movies
You say “I’ll meet you there in 20 minutes.”
Are you traveling at a constant rate for 20 minutes?
No, instead we average the speed. We went 5 miles in 20 minutes so what is my average speed to meet your friends at the movies?
.25miles/minute

8. Average vs. Instantaneous speed
During a typical trip to school, your car will undergo a series of changes in its speed. If you were to inspect the speedometer readings at regular intervals, you would notice that it changes often
The speedometer of a car reveals information about the instantaneous speed of your car.
Instantaneous speed- speed at a particular instant in time. (NOT AVERAGE SPEED)

9. Average vs. Instantaneous Speed
Average speed
Measure of distance traveled in a given period of time.
Ratio: distance per time

10. Average vs. Instantaneous speed
Suppose that during your trip to school you traveled a distance of 5 miles and the trip lasted 0.2 hours (12 minutes)
What is your average speed?
Average speed= 5 miles/0.2 hours= 25mph
What is your instantaneous speed?
Speed at the particular moment you looked at the speedometer

11. Formulas Speed= Distance/time How would average speed differ?
Average speed = Total Distance/Total Time

12. Problem 1:
If your great aunt Betty traveled 2500miles from LA to New York in 4 hours, what is the average speed of the airplane?

13. Problem 2: It takes you 9 minutes to run 1 mile.
What is your average speed in miles per minute?
In miles per hour?
.11 miles/minute
6.67 miles/hour