1. CHANGING POSITION
PHYSICS

2. Changing Position
If the position of an object is changing we say the the object has
velocity.

3. Position Graph
Slope = v x xo t

4. What is the definition formula for velocity
What is the definition formula for velocity? How does it relate to slope?
v = ∆x ∆t
rise = ∆x
run = ∆t
slope = ∆x ∆t

5. What are the UNITS of the slope. What do these units mean
What are the UNITS of the slope? What do these units mean? I move __ meters every second
rise = m
run = s
slope = m s

6. Steps for solving: STEPS: Identify what we know and want
Circle what we know
Underline what we want
Isolate the Variable
Plug it in & Solve

7. Position Formula:
y = m x + b
IS OFTEN ZERO x = v t + xo

8. WATCH OUT FOR MISMATCHED UNITS!!!

9. PRACTICE
1. Bob’s horse Chester can run 12 m/s. How many seconds will it take him to cross a football field (about 100 meters)?

10. PRACTICE
2. Susy jogs 3 m/s. If she jogs for half an hour, how many KILOmeters has she run?

11. PRACTICE
3. Bob lives 2 blocks (about 325 meters) from the high school. When he runs home for lunch it takes him 2 minutes and 10 seconds to get there. How fast can Bob run?

12. PRACTICE
4. Bob lives 3 miles from the high school. He usually obeys the speed limit (25 mph) but today he is running late so he decides to speed. He drives 35 mph. (BAD BOB!!) How much time (in minutes) does he save? Is speeding worth it? time without speeding = time with speeding = time saved =

13. PRACTICE
5. Geese can fly 12 m/s. How many days will it take them to migrate from Canada to Mexico (about 1600 miles)?

14. PRACTICE
6. Betty can only run 2 m/s. She needs to finish a 300 meter race in only 90 seconds. How much of a head start (in position) should we give her?

15. PRACTICE
7. A Great White Shark can swim 15 m/s. I can only swim 1.2 m/s. I am swimming at the beach and notice a dorsal fin 500 meters from the shore. How close to the shore do I need to be if I am going to escape? Time it takes the shark to reach the shore = Distance I can swim in that time =

16. PRACTICE
8. Billy is racing mealworms. His mealworm can run 2 cm/s. How much time will it take his mealworm to cross the football field (100 meters) if he gives it a 24 meter head start? (Give your final answer in hours.)

17. CHANGING VELOCITY
PHYSICS

18. Changing Velocity
If the velocity of an object is changing we say the the object has
acceleration.

19. Velocity Graph
Slope = a v vo t

20. What is the definition formula for acceleration
What is the definition formula for acceleration? How does it relate to slope?
a = ∆v ∆t
rise = ∆v
run = ∆t
slope = ∆v ∆t

21. What are the UNITS of the slope. What do these units mean
What are the UNITS of the slope? What do these units mean? Object gains __ m/s of speed every second
rise = m/s
run = s
slope = m/s s
= m s2

22. Types of Acceleration:
Speed up
Slow down
Turn

23. OFTEN EITHER V OR VO IS ZERO
Velocity Formula:
y = m x + b v = a t + vo
OFTEN EITHER V OR VO IS ZERO

24. PRACTICE
1. Daredevil David likes to race cars at the salt flats. His car can go from rest to 50 m/s in only 3 seconds. What is the acceleration of his car?

25. PRACTICE
2. The acceleration of gravity is about 10 m/s2. If I drop a rock off a cliff and it is in the air for 3.2 seconds, then how fast will it be moving when it slams into the ground?

26. PRACTICE
3. Susan was driving to school when a child ran in front of her car to grab a Frisbee. Her car was moving 17 m/s when she saw the child. Her brakes can accelerate -8 m/s2. She reaches the child 1.1 seconds later. Did she stop in time? If not, how fast was she still moving when she struck the child?

27. PRACTICE
4. Pedro is trying to get on the freeway. His car was only moving 10 m/s when he entered the on ramp. Freeway speeds require at least 25 m/s. If his engine can provide 3 m/s2 of acceleration, then how much time will it take him to reach freeway speeds?

28. PRACTICE
5. Wiley Coyote is chasing the Road Runner going 30 m/s. He notices a cliff in the distance. It takes him 2.8 seconds to come to a complete stop. What was his average acceleration? (Unfortunately, he stopped in mid air and so he will still plummet to his death.)

29. PRACTICE
6. Christine was driving home late at night when another car ran a red light and Christine hit them. The camera at the intersection caught the whole thing on video. Christine hit the other car 1.8 seconds after slamming on her brakes. Her brakes provide -7.5 m/s 2 of acceleration. When she hit the other car she was still moving 12 m/s. Christine has to appear in court. If the speed limit is 20 m/s, then is Christine going to get a ticket? Why or why not?