1. Usain Bolt is the world’s fastest man!!!

2. Physics of Motion We will look at:
Distance
Displacement
Speed
First you need to realize that motion is relative…

3. Motion is relative
What is meant by saying that motion is relative? For everyday motion, what is motion usually relative to?

4. Motion is Relative
Motion is relative to the observer’s position and their reference point
Sometimes called a “reference frame”
Consider the picture…
If this man is driving at 15 mph, how fast is his coffee cup moving?
Does the man feel like the cup is moving?
Why?

5. Motion is relative
An object is in motion if it changes position relative to a stationary reference point.

6. Direction
We use N, S, E, W to describe the direction of movement.

7. Distance and Displacement
Distance measures the actual path an object takes
Displacement measures your overall distance from the starting point in a STRAIGHT LINE.
DISPLACEMENT values must include a DIRECTION!
Which color line represents distance?
Displacement?

8. Distance vs. Displacement

9. Write in your own words- what is the difference between distance and displacement?

10. Speed Describes how fast an object moves.
We know some things move faster than others…but how do we measure it?
What two quantities must you know to determine speed?

11. What two quantities must you know to determine speed?
Choose from: displacement, distance, time, velocity
Hint…what is speed measured in???
Speed= distance/time
Ex- miles/hour, m/s, etc.

12. There are three types of speed you must know…
Constant speed
Average speed
Instantaneous speed

13. But first let’s look at some graphs…
If I wanted to graph speed, what should I label my axes???
So the slope of the line=SPEED
Distance
Speed
Time

14. Constant Speed
When an object covers equal distances in equal amounts of time
Ex- if a race car travels at a CONSTANT SPEED of 96m/s, it will travel a DISTANCE of 96 meters EVERY SECOND.

15. Constant Speed
What would a d-t graph look like for a constant speed?

16. But most objects do not travel at a constant speed.
The speed of an object can change from one minute to another.
So we can use AVERAGE SPEED to describe its motion.
Use this equation…
Average Speed = total Distance / total Time

17. Let’s try it
A runner finished a 3 mile race in 22 minutes. He may not have run at the same pace the whole time, but you can still calculate his AVERAGE SPEED
3 miles/22 minutes=.14 miles/min
PACE:
22 minutes / 3 miles = 7.33 min/mile

18. Instantaneous vs. Average speed
Average speed- overall distance over time the object traveled
Instantaneous speed- measures speed over small time interval (at an instant)

19. Does a speedometer of a car read instantaneous or average speed?

20. What 2 controls on a car enable a change in speed?

22. Let’s use our math skills
Page 323…
Read through “MATH SKILLS”
DO problems 1-3 “Practice Problems”

23. Answers to problems on 323 1. v=d/t 110m/72 sec= 1.5 m/s toward shore
38m/1.7 sec= 22m/s toward first base
d=vt=(12.0 km/hr)(5.00 hr)
= 6.00 x 104 m

24. What if I want to describe speed AND direction?
For example…what if you wanted to find a plane. Knowing the speed would only tell you how far away to look but not in what direction. For that we need…
VELOCITY- the speed and direction of motion.

25. Let’s get back to the car example…
Name another control that enables a change in velocity.

27. In order to analyze such situations, we need to understand what are known as vectors…
All measured quantities can be classified as being either a scalar or a vector.
Scalar
_________ only (size of the quantity ….a number)
Vector
_________ and _________
Magnitude
Magnitude
Direction

28. Speed is Velocity…kind of…
Velocity is the vector for the scalar of speed.
The magnitude is the same!!!
Therefore in calculations, you can use speed or velocity interchangeably
Speed = distance / time
Velocity = distance / time in a direction

30. Use the diagram to determine the resulting displacement and the distance traveled by the skier during these three minutes.

31. Answer The skier covers a distance of
(180 m m m) = 420 m and has a displacement of 140 m, rightward.

32. What is the coach's resulting displacement and distance of travel?

33. Answer The coach covers a distance of
(35 yds + 20 yds + 40 yds) = 95 yards and has a displacement of 55 yards, left.

34. How many meters will he travel in 5 seconds?
Consider a car moving with a constant, rightward (+) velocity of 10 m/s.
How many meters will he travel in 5 seconds?

35. Constant velocity

36. Now consider a car moving with a rightward (+), changing velocity - that is, a car that is moving rightward but speeding up or accelerating.

37. Acceleration

38. Distance time graphs Draw 2 graphs One showing a slow constant speed
One showing a faster constant speed

39. Slow, Rightward(+) Constant Velocity
Fast, Rightward(+) Constant Velocity
                                                                                       
                                                                                      

40. Slow, Leftward(-) Constant Velocity
Fast, Leftward(-) Constant Velocity
                                                                                     
                                                                                      

41. Consider a car moving with a constant, rightward (+) velocity - say of +10 m/s. A car moving with a constant velocity is a car with zero acceleration.
Draw a graph!

42. Constant velocity = zero acceleration

43. Now consider a car moving with a rightward (+), changing velocity - that is, a car that is moving rightward but speeding up or accelerating. Since the car is moving in the positive direction and speeding up, the car is said to have a positive acceleration.
                                                                                                                                      

44. Positive acceleration

45. Describe this graph!

46. Does the velocity of the wind affect such things as a sprinter’s speed or an airplane’s flight time?

47. Resultant Velocity animation

48. “Adding Vectors” Example:
A small airplane heads east with a speed of mph with respect to the air (the “air speed”). This would be the plane’s speed if the air was NOT moving – no wind)
If the wind/jet stream is moving east at 50 mph, what is the plane’s resulting velocity with respect to the ground (the “ground speed”)?
200 50
250 mph, east
with the wind

49. If, later, the airplane is flying west into the 50 mph wind with an “air speed” of 200 mph, now what is the plane’s resulting velocity with respect to the ground (the “ground speed”)?
200 50
150 mph, west
against the wind

50. Find the velocity in m/s of a swimmer who swims 110 m toward the shore in 72 s.

51. 1.5 m/s toward the shore

52. Imagine that you could ride a baseball that is hit high enough and far enough for a home run. Using the baseball as a reference frame, what does the Earth appear to do?

53. Calculate the displacement in meters a cyclist would travel in 5
Calculate the displacement in meters a cyclist would travel in 5.00 h at an average velocity of 12.0 km/h to the southwest.