1. Speed &
Velocity

2. Velocity (v): How fast an object is displaced.
Speed Vs. Velocity
Speed: How fast an object travels.
Velocity (v): How fast an object is displaced.

3. Concept Check
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REALLY?

4. Velocity is determined by displacement
Speed Vs. Velocity
They seem to be the same thing… right?
How are speed and velocity different?
Speed is determined by distance
Scalar
Velocity is determined by displacement
Vector

5. the ratio of the total distance traveled to the
Average Speed is:
the ratio of the total distance traveled to the
time taken to travel that distance d s = t
s = average speed
SI Units: m/s
d = total distance traveled
SI Units: m
Δt = change in time
SI Units: s

6. the ratio of change in position to the
Average velocity is:
the ratio of change in position to the
time taken to change the position x v = t
Δx = change in position (displacement)
SI Units: m
Δt = change in time
SI Units: s
v = average velocity
SI Units: m/s

7. The “sign” of the velocity indicates the direction of movement.
A positive sign indicates movement
in the positive direction.
A negative sign indicates movement
in the negative direction.

8. Units are Important!
What does meters mean?
What does mph mean?

9. Average Vs. Instantaneous
Think about it…
It took me 30 minutes to get the beach this summer.
Was I going the same velocity the whole time?
How did my velocity at a stop light compare to my velocity on the highway?
What’s the difference?

10. Practice: Easy
BYU’s running back, Jamaal Williams, runs the 40 yard dash in 4.46 s. What is his average speed in yd/s?
A speedometer shows his speed as he crosses the finish line to be 25.6 mph (12.47 yd/s).
Do you still believe your answer is correct? Why or why not?

11. Concept Check
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12. Practice: Difficult
Mr. Black runs west at 8 mph for 15 minutes, turns north and runs 7.5 mph for 20 minutes, stops to tie his shoes (which takes 5 minutes because he never learned in Kindergarten), and finally runs east for 5 minutes at 10 mph. What is his average speed and average velocity?

13. Solution
Remember, average speed is TOTAL DISTANCE divided by TOTAL TIME.
First you must calculate the distance for each part of the trip.
Use total distance and total time to find average speed.
Average velocity is DISPLACEMENT divided by TOTAL TIME.
First calculate Δx and Δy.
Calculate total displacement.
Calculate average velocity.