1. Physical Science - Physics
Motion
Forces
Work & Power
Thermal Energy
Light & Sound
Electricity & Magnetism

2. Distance, Speed, and Velocity
Motion:
Distance, Speed, and Velocity
Physical Science

3. Motion Motion = any change of position over a period of time.
Distance = length between two points.

4. How do you know an object is moving?
You must compare the object to other objects that are not moving.
You must have a frame of reference!
Frame of Reference: a set of objects that are not moving (a reference point).
“Relative to” means “compared to”

5. Frame of Reference
The arrows represent how fast each object is moving compared to the ground. How does each object “see” the other two as moving?

6. Frame of Reference
From the man’s frame of reference.

7. Frame of Reference
From the airplane’s frame of reference.

8. Frame of Reference
From the rocket’s frame of reference.

9. Frame of Reference Example Problems:
A gray car and a red car are traveling down the street at 35 mph.
For the driver of the grey car, does the red car appear to be moving?
If you were standing by the side of the road, how fast would the red car appear to be moving? No
35 mph

10. Frame of Reference
A red car is speeding down a neighborhood street at 45 mph. A police car is approaching the car and is traveling at a constant speed of 52 mph.
How fast is the police car moving relative to the ground?
How fast is the police car moving relative to the red car?
52 mph
7mph

11. Distance vs. Displacement
Distance: exact path traveled
Displacement: an object’s change in position
The straight-line distance from the start point to the end point.
Total distance traveled is always greater than or equal to displacement.
What are the units for distance/displacement?
Units: meters (m), kilometers (km), miles (mi), etc.

12. Displacement the distance an object has been moved from one
position to another

13. one car travels from one town to another that is 20 km to the east.
Example
one car travels from one town to
another that is 20 km to the east.
X→→→→→→→→→→→→→→→→→ X
20 km

14. another car travels around a track for 20 km and ends up at the
starting point. X

15. Both cars traveled a distance of 20
km but the first car’s displacement
is 20 km east while the second
car’s displacement is 0 km because
it ended up where it started from.

16. Some Conversion formulas you may need: Write these in your notes!!!!!
1 mile = km
1 km = .62 miles
1 mile = 5,280 feet
1 mile = 1,760 yards

17. Combining Displacements
You can add vectors using “vector addition”
When two displacements have the same direction, you can add their magnitudes.
Magnitude: size, length, amount
If two displacements are in opposite directions, the magnitudes subtract from each other.

18. Displacement along a Straight Line

23. Solve: Distance vs Displacement.

24. Displacement that isn’t along a straight path
When two or more displacement vectors have different directions, they may be combined by graphing.
The vector sum is called the resultant vector, it points direction from the starting point to the ending point.

25. Displacement that isn’t along a straight path
Suppose a person moves 3 meters from A to B and 4 meters from B to C as shown in the figure. The total distance traveled by him is 7 meters. But is he actually 7 meters from his initial position? No, he is only 5 meters away from his initial position i.e., he is displaced only by 5 m, which is the shortest distance between his initial position and final position.
Use Pythagorean’s Theorem!
a2 + b2 = c2

26. Distance vs Displacement

27. Example Problem
A car travels 3 miles east, 5 miles south, 3 miles west, and 1 mile north.
To solve, you can combine the displacements or you can draw a diagram.
What distance did the car travel? 12mi
What was the car’s displacement?
4mi
b) 12 miles
c) 4 miles, South

28. Solving using vector addition/subtraction
A car travels 3 miles east, 5 miles south, 3 miles west, and 1 mile north.
1) West and East are on the same axis (horizontal) so you can solve for the difference.
2) North and South are on the same axis (vertical) so you can solve for the difference. E 3
3-3 = 0 W 3 N 5
5-1 = 4 1 S

29. A car travels 3 miles east, 5 miles south, 3 miles west, and 1 mile north.4 5 1 3 S

30. Example Problem
A car travels 3 miles east, 5 miles south, 3 miles west, and 1 mile north.
What distance did the car travel? 12mi
What was the car’s displacement?
4mi
b) 12 miles
c) 4 miles, South

31. Example problems
What is the total distance of a person who over the course of a week ran a 5Km, 10Km, and biked a 150Km? Add all = 165Km
Julia drove 5.5 mi South to school today, and then drove 4.1 mi North to Samantha’s house after school. What was her total displacement? Subtract 5.5mi – 4.1mi = 1.4 mi

32. Magic Circle with units
Distance
(meters)
Time
(seconds)
Speed
(m/s)

33. Speed Speed = the rate at which an object moves.
Distance traveled per unit of time.

34. Any unit of distance divided by any unit of time is a unit of speed!
Most common unit for speed:
meters per second (m/s)
Can also be:
miles per hour (mi/hr)
kilometers per hour (km/hr)
feet per second (ft/s)
And so on…
Any unit of distance divided by any unit of time is a unit of speed!

35. distance traveled per unit time
Speed
rate of motion
distance traveled per unit time
Measured in meters per seconds m/s

36. Speed Measured in m/s If you travel 2m in 1 sec, what is your speed?
Car traveling at 80km/hr. What is this speed in m/s?
80 km x 1 hr x m = m/s
hr sec km

37. Constant speed = speed that does not change.
Example: Setting your cruise control on the interstate.

38. Average speed = total distance divided by total time
Example: Taking a road trip
Not constant speed (slow down for corners and speed up afterwards!)
But you still have an average speed!

39. Average Speed Total Distance Traveled = ? 1200 feet Total Time = ?3 4 5 6 7 8 9 10 11
20 seconds
300 feet
300 feet
Average Speed = ?
1200 ft / 20 s =
300 feet
60 ft/s

40. Instantaneous Speed
Instantaneous speed = speed at a given moment in time.
Example: Looking down at the speedometer while driving.
Can you see how your instantaneous speed and your average speed might not be the same?

41. These are SPEED GRAPHS – they show Dist / Time

42. Song time!

43. Velocity = speed in a given direction
Can change even when speed is constant!
MUST include direction with units
Example:
50 m/s = speed
50 m/s east = velocity
Scalar vs Vector
Scalar doesn’t have direction; vector does!
Speed = scalar
Velocity = vector

44. Speed/Velocity Equation
v = d t
Distance (d) – meters (m), kilometers (km), miles (mi)
Time (t) – seconds (s, sec), hours (h)
Velocity (v) – meters/second (m/s), kilometers/hour (km/h), miles/hour (mi/h)

45. Speed vs Velocity https://www.youtube.com/watch?v=WJHo_M_Ir3 A

46. Velocity Example Problems
Tonya decides to drive to the beach for a long weekend. The drive is 132 miles and it takes her 2.5 hours to get there. What was her velocity? If the speed limit was 65 mi/h, did she get a ticket? ____________

47. t d v d = 100 m v = d ÷ t t = 20 s v = (100 m) ÷ (20 s) v = ?
Calculations
Your neighbor skates at a speed of 4 m/s. You can skate 100 m in 20 s. Who skates faster?
GIVEN:
d = 100 m
t = 20 s
v = ?
WORK:
v = d ÷ t
v = (100 m) ÷ (20 s)
v = 5 m/s
You skate faster! v d t

48. t d v v = 330 m/s t = d ÷ v d = 1km = 1000m t = (1000 m) ÷ (330 m/s)
Calculations
Sound travels 330 m/s. If a lightning bolt strikes the ground 1 km away from you, how long will it take for you to hear it?
GIVEN:
v = 330 m/s
d = 1km = 1000m
t = ?
WORK:
t = d ÷ v
t = (1000 m) ÷ (330 m/s)
t = 3.03 s v d t

49. Velocity Problems that Require Conversions
Convert the distance or time unit so that it matches the velocity unit.
Example:
If your velocity is in m/s, your distance must be in ________ and your time must be in _______.

50. Metric Conversions 60 seconds = 1 minute 60 minutes = 1 hour
3600 seconds = 1 hour
1 meter = 100 centimeters
1 meter = 1000 millimeters
1 kilometer = 1000 meters
1 kilogram = 1000 grams

51. Velocity/Conversion Example Problems
How far does a car travel if it is moving at a speed of 15 m/s for 30 min?

52. Velocity/Conversion Example Problems (cont’d)
How long does it take a car to travel km at 20 m/s?
How long does it take a bicycle to travel 600 m at a rate of 12 km/h?

53. Find the Resultant Velocity
Resultant Velocity = Resulting or Net Velocity
Rules
If the velocities are in the same direction, add them.
If the velocities are in the opposite direction, subtract them.
The resultant velocity is in the direction of the larger velocity.

54. Examples
If you row a boat 5 km/hr down a river, the same direction that the river is flowing at 10 km/hr, your combined velocity is 15 km/hr downriver.
If you row the same boat 12 km/hr upriver, in the opposite direction that the river is flowing at 8 km/hr, then your combined velocity is 4 km/hr upriver.

55. Resultant Velocity Example Problems
A duck paddles up a river at 1.4 m/s. It is swimming against a current going 1.1 m/s. What is the resultant velocity of the duck?

56. Resultant Velocity Example Problems
2) A bus is traveling 12 m/s east. a) If a woman passenger walks towards the front of the bus at a rate of 1.5 m/s, what is the resultant velocity of the woman? b) After saying hi to the bus driver, she turns around and walks back toward the rear of the bus at the same speed. What is her resultant velocity now?

57. Check for Understanding
A car drives 400 km in 4 hours. What is the car’s average speed?
Answer: s = d/t
s = 400 km / 4 h
s = 100 km/h
A boat travels at a constant speed of 12 m/s for 50 seconds. How far does it travel?
d = st
d = (12 m/s)(50 s)
d = 600 m

58. Check for Understanding
A cat walks at a constant speed of m/s. How long does it take her to walk 75 meters?
Answer: s = d/t
st = d
t = d/s
t = (75 m)/(1.25 m/s)
t = 60 s

59. Speed is graphed on a distance / time graph
Distance / Time Graphs
Speed is graphed on a distance / time graph
The slope of the line is the speed
Constant speed will be a straight line
Horizontal lines on a distance / time graph indicate the object has stopped.

60. Distance Time Graphs

61. slope = speed steeper slope = straight line = flat line = faster speed*
07/16/96
Graphing Motion
Distance-Time Graph A B
slope =
steeper slope =
straight line =
flat line =
speed
faster speed
constant speed
no motion *

62. The graph shows an object which is not moving (at rest).
The distance stays the same as time goes by because it is not moving.

63. The graph shows that the objects distance increases as time passes
The graph shows that the objects distance increases as time passes. The object is moving and so it has velocity.
The line is straight, showing that the velocity is constant (not changing).

64. Just like the previous graph, this graph shows an object moving with constant velocity.
The negative slope does NOT mean that it is slowing down. The negative slope means it is moving TOWARD you.

65. In the first part of the graph the object is moving with constant velocity.
In the second part of the graph the object is at rest (not moving).
In the third part the object is again moving with constant velocity.

66. What is the objects’
average speed?
What is its speed
between 6s and 10 s?
When is it traveling
the fastest?
When is it NOT
moving?

67. Where is the object
standing still?
traveling backwards?
traveling at 5m/s?
What is speed at line E?

68. https://www.youtube.com/watch?v=ZM8ECpBuQ YE
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