1. Today I will differentiate between distance and displacement
10/14/16
Today I will differentiate between distance and displacement
Warm Up. If I travel 40 miles in 2 hours, how fast have I gone?

2. Linear Motion
Chapter 2 (part 1)

3. Motion is relative Is this book moving? In relation to the desk
In relation to the sun

4. Linear motion
What is linear motion?
Motion in a straight line

5. Scalar vs. Vector Quantities
Scalar Quantity – a quantity that needs magnitude only (no direction)
Vector Quantity – a quantity that requires both a magnitude and a direction.
Magnitude – the “how much” in a number
Ex. 35 m/s in a northern direction

6. Distance vs. Displacement
How far you have traveled total
Displacement -
How far you have traveled away from your starting place – in some direction
Change in position (final – initial)

7. Vector Quantities Distance is a SCALAR quantity
Displacement is a VECTOR quantity

8. Distance vs. Displacement
Distance and displacement will be the same magnitude for most of this class.
Magnitude means the number (not the direction)
HOW??
We will usually be discussing motion in a straight line!

9. Today I will calculate speed and velocity
Warm Up –
A dog named Goldie runs to the park 500 m from his house. From there, he runs to his dog- friend’s house another 1000 m from the park. The two dogs then go back to the park to play. When they are done playing, Goldie walks back home. What is Goldie’s total distance and displacement for the day?

10. What is a “rate”?
A quantity divided by time

11. Speed Define speed Change in Distance Time
The rate that something moves with
Speed =
Change in Distance
Time
Question: If I travel 20 miles in 4 hours, what is my speed?

12. Speed
Average speed
How fast you are moving over the course of some distance

13. Speed Instantaneous speed
How fast you are moving at that moment
I live about 35 miles from school and it takes me about an hour to get here.

14. Velocity Define Velocity Displacement Time Speed in a given direction
60 miles per hour
- speed
60 miles per hour North
- velocity

15. Speed vs Velocity
Yesterday, we said in our class, distance and displacement will often be the same.
What about speed and velocity?
Again, same with the exception of adding direction.

16. Speed/Velocity
What about the units?
Distance
Time

17. Vector Quantities Distance is a SCALAR quantity
Displacement is a VECTOR quantity
Speed is a SCALAR quantity
Velocity is a VECTOR quantity

18. Solved Examples
Benjamin watches a thunderstorm from his apartment window. He sees the flash of a lightning bolt and begins counting the seconds until he hears the clap of thunder 10. s later. Assume that the speed of sound in air is 340 m/s. How far away was the lightning bolt a) in m? b) in km?

19. Solved Examples
On may 28, 2000, Juan Montoya became the first Colombian citizen to win the Indianapolis Montoya completed the race in a time of 2.98 h. What was Montoya’s average speed during the 500. mi race?

20. Solved Examples
The slowest animal ever discovered was a crab found in the Red Sea. It traveled with an average speed of 5.70 km/y. How long would it take this crab to travel 100. km?

21. Solved Examples
Tiffany, who is opening in a new Broadway show, has some limo trouble in the city. With only 8.0 minutes until curtain time, she hails a cab and they speed off to the theater down a m. long one-way street at a speed of 25 m/s. At the end of the street, the cab driver waits at a traffic light for 1.5 min and then turns north onto a m long traffic-filled avenue on which he is able to travel at a speed of only 10.0m/s. Finally, this brings them to the theater. a.) Does Tiffany arrive before the theater lights dim? B.) Draw a distance vs. time graph of the situation.

22. Homework
Exercises 1-4

23. Today I will calculate acceleration
Warm Up – If I drive 350 miles on a trip at an average of 60 miles/hour, how long will it take me?

24. Homework - Exercise 1
Hans stands at the rim of the Grand Canyon and yodels down to the bottom. He hears him yodel echo back from the canyon floor 5.20 s later. Assume that the speed of sound in air is m/s. How deep is the canyon floor at this point?

25. Homework - Exercise 2
The world speed record on water was set on October 8, by Ken Warby of Blowering Dam, Australia. If Ken drove his motorboat a distance of m in 7.045s, how fast was his boat moving a) in m/s? b) in km/h?

26. Homework - Exercise 3
According to the World Flying Disk Federation, on April 8, 2000, Jennifer Griffin of Fredericksburg, VA threw a Frisbee for a distance of m to capture the women’s record. If the Frisbee was thrown horizontally with a speed of 13.0 m/s, how long did the Frisbee remain aloft?

27. Homework - Exercise 4
It is now 10:29 am, but when the bell rings at 10:30 am Suzette will be late…She runs down the first hallway, a distance of m, at a speed of 3.50 m/s. The second hallway is filled with students, and she covers its 48.0 m length at an average speed of 1.20 m/s. The final hallway is empty and Suzette sprints its 60.0 m length at a speed of 5.00 m/s. Is she late?

28. Velocity Constant Velocity Changing Velocity
Both a constant speed AND direction
Changing Velocity
Change in speed OR direction

29. Acceleration – changing velocity
EITHER speed or direction!
Acceleration is a VECTOR so it needs direction!
Acceleration =
Change in Velocity
Time

30. Acceleration
vf = final velocity, vi = initial velocity

31. Acceleration What are the units on acceleration?? Acceleration =
Acceleration = m/s2
Change in velocity
time
m/s s

32. Acceleration Concept Check
Acceleration is a rate that describes how much the velocity of a car changes in a time period.

33. Acceleration Concept Check
If a car is accelerating at 10 m/s2, it means that the car’s velocity will increase 10 m/s in each second.
If that car starts at rest, how fast will it be going after 1s? After 5 s?
What if the car is going at a constant velocity? What is the acceleration?

34. Can acceleration be negative?
When you round a bend at a constant speed are you accelerating?

35. Example 5
Grace is driving her sports car at 30 m/s when a ball rolls out into the street in front of her. Grace slams on the brakes and comes to a stop in 3.0s. What was the acceleration of Grace’s car?

36. Today I will determine distance traveled with acceleration.
Warm Up-
How much distance do you travel if you are driving at 70 m/s for 2.0 hours?

37. Symbols in physics d = distance ∆d = displacement (change in position)
We use lots of letters and symbols in physics equations
d = distance
∆d = displacement (change in position)
s = average speed
t = time
v = average velocity
∆v = change in velocity
vi = initial velocity (also seen as vo)
vf = final velocity (also seen as v)
a = acceleration

38. Distance

39. Homework - Exercise 5
A jumbo jet taxiing down the runway receives word that it must return to the gate to pick up an important passenger. The jet is traveling at 45.0 m/s when the pilot receives the message. What is the acceleration of the plane if it takes the pilot 5.00 s to bring the plane to a halt?

40. Homework - Exercise 6
While driving his sports car at 20.0 m/s down a four lane highway, Eddie comes up behind a slow moving dump truck and decides to pass it. If Eddie can accelerate at 5.00 m/s2, how long will it take for him to reach a speed of 30.0 m/s?

41. Homework - Exercise 7
Vivian is walking to the hairdresser’s at 1.3 m/s when she realizes she is late. Vivian gradually quickens her pace at a rate of m/s2. a) What is Vivian’s speed after 10.0 s? B) Is she walking, jogging, or running very fast?

42. Distance – Constant Velocity
If I drive 50 miles per hour, how much distance have I covered in the first hour? In the second hour? Third?

43. Distance – Constant Velocity
At constant velocity, the ball covers the same amount of distance in the same amount of time.

44. Acceleration and Constant Velocity Review
A girl is standing at rest. She then accelerates at 1 m/s2 for 5 seconds. Chart her velocities.

45. Distance
When a ball accelerates, it covers more distance with each passing time interval.
*Note: This book equation d=1/2at2 works for constant acceleration starting from rest.

46. Distance

47. Distance Problems
An airplane starting from rest accelerates down a runway at 3.20 m/s2 for 32.8 s until is finally lifts off the ground. Determine the distance traveled before takeoff.
A car starts from rest and accelerates uniformly over a time of 5.21 seconds for a distance of 110 m. Determine the acceleration of the car

48. Distance Problems
An ice skater staring from rest accelerates to 26 m/s in 2 seconds. How much ground has he covered?