1. MOTION

2. When is an object in motion?
An object is in motion when its distance from another object is changing.

3. How do you determine when an object is in motion?
By using a reference point.
A reference point is a place or object used for comparison to determine if something is in motion.

4. Are distance and displacement of an object the same?

5. Distance and Displacement
Distance is a scalar quantity that refers to "how much ground an object has covered" during its motion.
Displacement is a vector quantity that refers to "how far out of place an object is"; it is the object's overall change in position.

6. Distance and Displacement
A physics teacher walks 4 meters East, 2 meters South, 4 meters West, and finally 2 meters North.
Distance Traveled?
12 meters
Displacement?
0 meters

7. The diagram below shows the position of a cross-country skier at various times. At each of the indicated times, the skier turns around and reverses the direction of travel. The skier moves from A to B to C to D. Determine the resulting displacement and the distance traveled by the skier during these 3 minutes.
Distance Traveled?
420 meters
Displacement?
140 m, rightward or east

8. A football coach paces back and forth along the sidelines
A football coach paces back and forth along the sidelines. The diagram below shows several of the coach’s positions at various times. At each marked position, the coach makes a “U-turn” and moves in the opposite direction. The coach moves from A to B to C to D.
Distance Traveled?
95 yards
Displacement?
55 yards, leftward or west.

9. Check Your Understanding
What is the displacement of the cross-country team if they begin at the school, run 10 miles and finish back at the school?
0 miles
What is the distance and the displacement of the race car drivers in the Indy 500?
Displacement =
0 miles
Distance =
500 miles

10. Scalars and Vectors
To understand the distinction between distance and displacement, you must understand vector and scalar quantities.
Scalars are quantities, which are fully described by magnitude (or numerical value) alone.
Vectors are quantities, which are fully described by both a magnitude and a direction.

11. Scalar or Vector? 5 meters 30 m/sec, East 5 mi., North
20 degrees Celsius
256 bytes
4000 calories
Scalar Vector

12. How can motion be described?

13. By using a reference point – A (usually) stationary object that helps you detect the motion of an object. (Ex. tree, house etc.)

14. Once the reference point is determined you can define motion by speed, position, and direction.

15. What is speed?

16. Speed refers to how fast an object travels
Speed refers to how fast an object travels. (Rate at which an object moves.)
Depends on:
Distance
Time
Scalar Quantity

17. Various forms of speed:
Instantaneous– speed at a given moment (speedometer)
Constant– speed that doesn’t change (cruise control)
Changing– speed that varies (running a mile)

18. Formula for objects moving at a constant rate.
Calculating Speed
Formula for objects moving at a constant rate.
Speed = distance
time
Scalar Quantity

19. Average – speed is the distance per time ratio. Formula: Average Speed
= Total distance traveled
Total time
Scalar Quantity

20. Ex. If you ran the distance of a football field (91 meters) in 30s, would you run the same speed from start to finish?
No, you find the average speed you ran.

21. Average Speed
= Total distance traveled
Total time
= 91m
30s
= 3.03 m/s

22. THEY HAVE DIFFERENT VELOCITIES
Two cars traveled at 50 km/h on the same highway. After 2 hours the cars are 200 km away from each other. How is this possible?
THEY HAVE DIFFERENT VELOCITIES

23. Would you rather know the hurricane’s speed or velocity?
What is velocity?
Would you rather know the hurricane’s speed or velocity?

24. Velocity –speed of an object in a particular direction.
Velocity changes when speed or direction of an object changes.
Vector Quantity

25. Average Velocity – the displacement or position change per time ratio.
Vector Quantity

26. Can you have a constant speed but a changing velocity?

27. Yes, the Ferris wheel can be moving at a constant speed but its constantly changing direction!

28. Check Your Understanding
While on vacation, Trevor Mobley traveled a total distance of 440 miles. His trip took 8 hours. What was his average speed?
Average Speed = Total distance/Total time
Average Speed = 440 mi/8hr
= 55 mi/hr

29. Check Your Understanding
A physics teacher walks 4 meters East, 2 meters South, 4 meters West, and finally 2 meters North. The entire motion lasted 24 seconds.
Average Speed?
12 m/24s = .50m/s
Average Velocity?
0 m/s

30. The diagram below shows the position of a cross-country skier at various times. At each of the indicated times, the skier turns around and reverses the direction of travel. The skier moves from A to B to C to D. Determine the average speed and the average velocity of the skier during these 3 minutes.
Average Speed?
420 m/3 min = 140m/min
Average Velocity?
140 m, east/3min = 46.7 m/min, east

31. A football coach paces back and forth along the sidelines
A football coach paces back and forth along the sidelines. The diagram below shows several of the coach’s positions at various times. At each marked position, the coach makes a “U-turn” and moves in the opposite direction. The coach moves from A to B to C to D.
Average Speed?
95yd/10 min = 9.5 yd/min
Average Velocity?
55 yd, left/10min = 5.5 yd/min, left

32. In conclusion
Speed, being a scalar quantity, is the rate at which an object covers distance.
The average speed is the distance (scalar) per time ratio.
Velocity is the rate at which the position changes (vector quantity).
The average velocity is the displacement or position change (vector quantity) per time ratio.

33. How can you graph speed?

34. How is acceleration related to velocity?

35. Acceleration – rate of change of speed (velocity)
Occurs when an object changes:
Increase speed
Decrease speed
Direction

36. What are the types of acceleration?

37. Positive Acceleration – speeding up
Negative Acceleration – slowing down

38. How do you find acceleration?
Formula:
a= vf –vi t

39. What are velocity/time graphs?
Shows change in velocity over time (acceleration).

40. Moving at a constant velocity

41. Moving at a positive acceleration – velocity changing at constant rate.

42. Moving at a negative acceleration – velocity changing at constant rate.

43. What is centripetal acceleration?

44. Acceleration that occurs in a circular motion; object traveling in a circle is constantly changing directions; so acceleration occurs continuously

45. FORCES

46. S8P3. Students will investigate relationship between force, mass, and the motion of objects.
b. Demonstrate the effect of balanced and unbalanced forces on an object in terms of gravity, inertia, and friction.

47. What is a force?

48. A force is a push or pull that one body exerts on another.
Ex. Friction, gravity, kicking a football.
Unit: Newton (N)

49. What is a net force?

50. The sum of the forces acting on an object.

51. What is a balanced force?

52. When the forces acting on the object are equal in size and opposite in direction.
Net force = 0 (forces cancel each other out)
No change in motion occurs!!

53. What is an unbalanced force?

54. Occurs when forces acting on the object are unequal.
Net Force is in the direction of the larger force. (object will move in that direction)

55. What is the difference between balanced and unbalanced forces?

57. You Try It: Net Force
16N
10N
20N
0 N 4N
0 N

58. What is Newton’s 1st Law of Motion state?

59. An object in motion will stay in motion unless an outside force acts upon it.
An object at rest will stay at rest unless an outside force acts upon it.

60. What is another name for the 1st Law?
The Law of Inertia

61. What is Inertia?

62. The tendency of an object to resist change.

63. Which has a greater inertia?

64. Elephant – inertia depends on mass!!

65. What does Newton’s 2nd Law state?

66. Acceleration depends on the objects mass and on the net force acting on the object.

67. What is the relationship between force, mass, and acceleration?

68. Force and Acceleration
The greater the force applied to an object the greater the acceleration will be.

69. Force and Mass Acceleration will be less on a object that is heavier.
Ex. Softball v. Baseball

70. An object will accelerate in the direction of the net force.
F = m x a, a = F/m,
m = F/a

71. What is the unit for force?
Newton
kg x m/s/s

72. Types of Forces

73. What is a force that opposes motion between 2 moving objects?

74. FRICTION

75. What does the amount of friction depend on?

76. The strength of the force of
friction depends on two
factors:
1. how hard the surfaces
push together and
2. the types of surfaces
involved.

77. What is static friction?
Friction between two surfaces that are not moving past one another.

78. What is sliding friction?
Force that opposes motion of 2 objects sliding past one another.

79. What is Rolling Friction?
Opposing motion between two objects rolling past each other.

80. What is Fluid Friction?
Friction that occurs as an object moves through fluid.

81. How is friction helpful?

82. Without friction the tires could not push against the ground to move the car forward and brakes couldn’t stop the car.

83. How can you reduce friction?

84. Lubricants – are used to reduce friction.
Ex. Motor oil, wax, grease
Switching from sliding to rolling friction
Ex. Ball bearings between wheel & axles

85. What is Gravity?

86. A downward force
Any 2 masses exert an attractive force on each other.
Strength of gravitational force depend on:
1.) Mass
2.) Distance

87. What is the law of universal gravitation?
All objects are attracted to each other by gravitational force.
The larger the object – The greater the force
The closer together the object – the greater the force.

88. Is weight a force?

89. Weight is considered to be a gravitational force that decreases as you move from Earth.

90. What is the difference between mass and weight?

92. Mass – how much matter makes up an object
(Doesn’t change as you move from the Earth to the moon.)
Weight – considered to be a gravitational force
(Decreases as you move from the Earth to the moon.)

93. Free Fall Free fall occurs when the only force
acting on an object is gravity.
An object in free fall is accelerating.
In free fall, the force of gravity is an
unbalanced force, which causes an
object to accelerate.

94. What is acceleration due to gravity?

95. Anything that falls through the air falls at an acceleration of 9
Anything that falls through the air falls at an acceleration of 9.8m/s/s.
This means that for every second an object is falling, its velocity increases by 9.8 m/s.

96. What is Air Resistance?

97. Effects anything that is in Earth’s atmosphere.
Upward force that opposes gravity of anything falling through the air.

98. Air Resistance Depends on 3 things:
1. SPEED
2. SIZE
3. SHAPE
of an object.

99. If there were no air resistance a hammer and feather would fall at the same time.

100. What is a projectile?

101. Anything that is thrown or shot through the air.

102. Why do projectiles follow a curved path?

103. They follow a curved path due to pull of gravity.
Ex: An arrow, Bullet, Basketball

104. What is Newton’s 3rd Law of Motion?

105. When one object exerts a force on a second object, the second one exerts a force that is equal and in size and opposite in direction.
“Action/Reaction Occurs

107. What is Momentum?

108. Momentum = mass x velocity p= m x v
Momentum is related to how much force is needed to change an object’s motion.
Momentum = mass x velocity
p= m x v

109. What is the law of conservation of momentum?

110. Momentum can be transferred from one object to another
The total momentum of any group of objects remains the same, or is conserved unless outside forces act on the objects.

111. What is the relationship between mass and velocity?
If two trucks have same velocity, but different masses then . . .
the truck with the larger mass has more momentum