1. Bellringer 9.4.14 1. How is velocity different from speed?
2. Which two factors (variables) determine an object’s velocity?
3. Guess which graph below shows a constant velocity A or B?

2. Instantaneous Speed Speed can be measured at a certain point in time.
For instance, if you are driving, your speedometer may read 30 mi/hr.
You don’t have to drive for an hour for your car to know this – your speed is instantaneous.

3. Velocity (Speed)
Speed is a rate for the distance traveled per unit of time
Velocity is speed in a direction
Velocity = Distance
Time
Measured in m/s (meters per second) d V t

4. Calculating Velocity
After driving for exactly 60 seconds, you have driven 600 meters. What velocity were you driving?
V= d/t d=600m t= 60s v= 600m
60s
v= 10 m/s

5. Calculating Velocity / Time / Dist.
You know you can drive
80 km/hr to get to the concert. The concert is 470 km away. How long will it take for you to get there?
V= d/t t= ? v=80 km/hr d=470
80=470/t t=470/ t= 5.88 hrs

6. Constant Velocity
Constant Velocity - means an object does not speed up or slow down.
Which car is moving fastest? Which is moving at a constant speed?

7. Graphing Constant Speed

8. How to read a Constant Velocity Graph

9. Motion Maps
Pretend you are eating a dripping ice cream cone while you are walking
What kind of motion do the drips mean?

10. Acceleration Acceleration occurs when an object: Speeds up Slows down
**Changes direction**

11. Acceleration
Acceleration is the rate of change of velocity

12. Graphing Changing Speed

13. Graphing Changing Speed

14. Acceleration Acceleration is found by: a = (vf – vi) time
The units are m/s2

15. Calculating Acceleration
A car goes from 0 m/s to 20 m/s in 6 s. What is the car’s acceleration?
Vf= 20m/s
Vi = 0m/s
T=6s
a = vf-vi t
a= 20-0 = 3.33m/s² 6

16. Calculating Acceleration
2. A man was running at 3 m/s. In 4 seconds, he slowed down so his velocity is now 1 m/s. What was his acceleration?
Vf= 1m/s
Vi = 3m/s
T= 4s
a = vf-vi t
a= 1-3m/s = -0.5m/s² 4s

17. Finding Unknowns with Acceleration
3. A bobcat starts running at 30m/s and his acceleration is 5m/s/s. What would his final velocity be if he ran for 5 seconds?
Vf= ?
Vi = 30m/s
T= 5s
a= 5m/s²
a = vf-vi t
5m/s² = Vf—30m/s 5s
25=vf =vf

18. A girl is riding her skateboard to the park, and she started out going 5m/s but by the time she got down the hill, she was going 22m/s. If her acceleration was 3m/s², how long did she ride the skateboard?