1. Today’s Activities Warm-up Think, Pair, Share Notes Forces questions
Complete worksheet you picked up on your way in
Think, Pair, Share
Notes
Forces questions

2. Think, pair and share…
What would happen if both people pushed in the opposite direction? Why?
What happens when the people are pushing in the same direction? Why?
Write your answers in your journal and then share with your partner.

3. FORCES

4. A FORCE IS A OR
Forces are measured in Newtons (N)

5. A
In a force diagram, a force may be represented by an arrow (shows the direction in which the force is acting) B D C

6. Force Diagrams
A force may be represented by an arrow. Since forces have both direction and magnitude (size), the length or the thickness of the arrow will give you a relative idea of the size of the force. A B D C

7. FORCES CAUSE CHANGES IN MOTION
              
In order for a motion to start, stop, speed up, slow down, or change direction you must have a force.

8. Forces cause changes in motion
Describe how you used force to create changes in the car’s motion

9. Forces cause changes in motion
What did you do to start your car moving?
Pushed it – applied a FORCE
What did you do to stop your car?
Pushed or pulled it – applied a FORCE
What did you do to change your car’s direction?
Pushed it from the side – applied a FORCE
What did you do to speed your car up?
Pushed it in the direction it was already going – applied a FORCE

10. What are some common forces?
Types of Forces
Gravitational force (Gravity)
Friction
Applied force
Net force
Balanced force
Unbalanced force

11. Gravitational Force (Gravity)
The force of attraction between objects that is due to their mass is called gravity.
It is what makes things fall to the ground on Earth.

12. Gravity also holds Earth and the other planets in their orbits around the Sun.

13. Gravitational Force (Gravity)
The force of gravity also exists on the Moon but it is not as strong as it is on the Earth.
This is because the mass of the Moon is much lighter than the mass of the Earth.

15. What Does the Pull of the Moon Do to the Oceans?

16. Gravity Keeps Satellites in Orbit Around Earth
A satellite is an object that moves around larger object. The Earth and the moon are “natural satellites. Usually satellites are man-made. They and are sent into space to help scientists learn about the Earth, the solar system and the universe. Other satellites monitor weather, send TV signals and phone calls around the world.

17. Planet A has two times as much mass as Planet B
Planet A has two times as much mass as Planet B. How will the gravity on the planets compare?
The gravity on Planet A will be twice that of Planet B.
An astronaut could jump half as high on Planet A.
On Planet A it takes twice the amount of force to jump the same height as on Planet B.
Planet A
Planet B

18. Mass vs. Weight
The mass of an object is how much matter it contains. It is measured in grams (g) or kilograms (kg) but is NOT a force.
The weight of an object is the force caused by gravity pulling down on the mass of an object. It is measured in Newtons (N).

19. Spring scale, spring balance, Newtonmeter or forcemeter
Used to measure forces in Newtons (N)
Weight is measured using a springscale.
The bigger the weight attached to the springscale, the more the spring inside the springscale stretches.

20. Question
A push or a pull of an object is called a ______________________

21. Answer
Force

22. Question
Forces are measured in units called _____________________

23. Answer
Newtons

24. Question
When the forces are balanced, what happens to an object?

25. Answer
The object is at rest.

26. Question Forces can change the: Speed of objects only
Speed, direction or shape of an object
Movement of objects only if they are already in motion.

27. Answer
B: speed, direction or shape of an object

28. Question An example of unbalanced forces in action is:
A boat floating on still water.
A person sitting on a chair
A rising balloon

29. Answer
C. a rising balloon.

30. Question
What happens if a force is unbalanced?

31. Answer
It begins to move

32. Question
Name two types of forces

33. Answer
Gravity
Friction
Applied
Net
Unbalanced
Balanced

34. Question
Who has more gravity pulling down on them, and elephant or a dog?

35. Answer
Elephant

36. Question
True or false: an object at rest has forcing acting on it.

37. Answer
True

38. Today’s Activities Warm-up Force diagrams Simulation lab
What do the arrows in a force diagram represent? Give three examples
How does mass affect gravity?
What is a force?
Force diagrams
Simulation lab

39. Force on an inclined plane
Statement of the Problem:
How does the angle of the inclined plane affect the amount of force needed to move the car up the ramp?
Independent (manipulated) Variable:
Dependent (responding) Variable:
What should you keep constant?
Angle of the inclined plane
Force needed to move the car
Distance
Mass
Acceleration

40. Force on an inclined plane
How does the mass of the car affect the amount of force needed to move the car up the ramp?
Independent (manipulated) Variable:
Dependent (responding) Variable:
What should you keep constant?
Mass of the car
Force needed to move the car
Distance
Angle of inclined plane
Acceleration

41. Force on an Inclined Plane
You have a car on an inclined plane.
Attach the spring scale to the front of the car.
Attach different amounts of mass to the car and measure the force it takes to move the car 10 cm at different angles

42. Force on an Inclined Plane
How did the angle of the inclined plane affect the amount of force needed to pull the car? 
How did the mass of the car affect the amount of force needed to pull the car?
The larger the angle/steeper the incline, the more force needed to pull the car
The larger the mass of the car, the more force needed to pull it

43. Today’s Activities Warm-up Discuss simulation lab Notes/ Activities
Name three different types of forces.
Draw a force diagram for a person moving a box
Draw a force diagram for a person trying to move a car.
Discuss simulation lab
Notes/ Activities

44. Balanced Forces
When two forces acting on an object are equal in size but act opposite in direction, we say that they are balanced forces.
Balanced forces do not change motion.

45. Balanced Forces
If the forces on an object are balanced (or if there are no forces acting on it) this is what happens:
an object that is not moving stays at rest
an object that is moving continues to move at the same speed and in the same direction

46. Hanging Objects
The forces on this hanging crate are equal in size but act in opposite directions. The weight pulls down and the tension in the rope pulls up.
The forces on this hanging crate are balanced.

47. Floating in Water
Objects float in water when their weight is balanced by the upthrust, or buoyancy, from the water. The object will sink until the weight of the water it pushes out of the way is the same as the weight of the object.
A boat floats because its weight is balanced by the upthrust from the water.

48. Buoyancy – a force that pushes up objects immersed in fluids.
Float
Hover
Sink

50. Balanced Forces

51. Hammer Balance
QUESTION: How is the ruler balanced on the edge of the table?
The forces on the ruler are balanced.
The force from the handle of the hammer (its weight) is pushing up with equal and opposite strength as the force of gravity is pulling down on the ruler.

52. Unbalanced Forces
Unbalanced forces change the way something is moving. Unbalanced forces can make objects start to move, stop moving, speed up, slow down, or change direction.
When two forces acting on an object are not equal in size, we say that they are unbalanced forces.
If the forces on an object are unbalanced this is what happens:
an object that is at rest starts to move
an object that is moving changes speed or direction

53. Unbalanced Forces Unbalanced forces always cause a change in motion.
They are not equal
OR they are not opposite.

54. Unbalanced Forces

55. Two important things to remember:
forces in the same direction combine by addition
2) forces in opposite directions combine by subtraction.

57. Balloon Rocket
As more air escapes from a balloon, it will travel a greater distance on a string.
Independent (manipulated) Variable:
-Amount of propellant (air) in the balloon
Dependent (responding) Variable:
-Distance the balloon travels

58. Balloon Rocket
As more air was added to the balloon, what happened to the distance it traveled on the string?
As more air was added to the balloon, it traveled a greater distance on the string.

59. Balloon Rocket Explanation:
The forces acting on the balloon when it is at rest are balanced.
The forces acting on the balloon when it is moving are unbalanced.
The air inside the balloon is the source of the force making the balloon move.
The more air that is added, the more the balloon will move on the string.

60. Are there different forces acting on the figure skaters?
What direction are the forces acting?
Are the forces balanced or unbalanced? How do you know?

61. When a satellite orbits earth are the forces balanced or unbalanced?

62. Applied Force
Force applied to an object by a person or another object

63. Applied Force The applied forces on the box are: 20 N to the right
20 N to the left
The forces on the box are balanced.
QUESTION: Is the box in motion?

64. The image below shows a force of 10 N being applied to an object.
APPLIED FORCE
The image below shows a force of 10 N being applied to an object.
No other force is acting on the object.
The force is being applied toward the right, so the object is accelerating to the right.

65. Net Force
The size of the overall force acting on an object is called the net force.
If the forces are balanced, the net force is zero.
If the forces are unbalanced, the net force is the difference between the two forces.
Net Force = 0 N

66. Net Force is the combined effect of all forces acting on an object.

67. Net Force
The applied forces are 20 N to the right and 40 N to the left
The net force on the box is 20 N to the left.
QUESTION:
Is the box in motion?
In which direction?

68. Net Force is the combined effect of all forces acting on an object.

69. Net Force is the combined effect of all forces acting on an object.

70. If the force that is exerted is equal and opposite, the two forces cancel each other out and the resulting force is zero newtons.
Will there be a change in motion? NO
Are the forces balanced or unbalanced?
BALANCED

71. Tug of War
QUESTIONS:
Who is applying more force? Which direction is the rope going in?

72. In a tug of war the forces are moving away from each other
In a tug of war the forces are moving away from each other. If the two teams have equal strength, or force, the rope will stay pretty much in the same place. It would look like this.
What is the net force?
0 N
Would there be a change in motion? NO

73. Does the diagram represent balanced or unbalanced forces?
The arrows are pointing in directly opposite directions, therefore the forces are directly opposite each other
The arrows are the same size, therefore the forces are the same size
Since the forces are equal and opposite, they are BALANCED

74. Does the diagram represent balanced or unbalanced forces?
The arrows are pointing in directly opposite directions, therefore the forces are directly opposite each other
The arrows are different sizes, therefore the forces are different sizes
There is a net force to the left. The forces are UNBALANCED.

75. Coin Drop What do you think will happen to the coin?
Describe the forces acting on the coin and motion of the coin
Why did the coin move the way it did?
Question to think about: What would happen to the coin if you pulled the card very slowly?

76. Friction
Whenever an object moves against another object, it feels frictional forces.
These forces act in the opposite direction to the movement.
Friction makes it harder for things to move (e.g. easier to move on ice than on sandpaper).

77. Friction Friction can be useful:
Friction can be useful:
Friction between our shoes and the floor stop us from slipping
Friction between tires and
the road stop cars from
skidding

78. Air Resistance is a Type of Friction
Air resistance is caused by the frictional forces of the air against an object.

79. Paper Drop
As the surface area of the paper decreases, the speed with which it falls increases.
Independent (manipulated) Variable:
Dependent (responding) Variable:
Surface area of paper
Air resistance on paper

80. Paper Drop Explanation:
Since the surface area of the crumpled paper is less that the uncrumpled piece of paper, it experienced less air resistance, so it fell faster.
QUESTION: What would happen if you placed a book under the uncrumpled piece of paper and then dropped it? Why?

81. Coin Drop Revisited
What do you think will happen to the coin when you pull the card slowly from the side?

82. Coin Drop Revisited What happened to the coin?
It did not fall in the cup
Describe the forces acting on the coin and motion of the coin
Gravity acting downward and Friction acting in the direction of the card’s motion  the coin moved with the card
Why did the coin move the way it did?
The force of friction between the card and the coin made the coin move with the card

83. Frictional Forces of Different Surfaces
As the friction between an object and the surface increases, the force it takes to move the object across the surface increases.
Independent (manipulated) Variable:
Dependent (responding) Variable:
Amount of friction between the block and the surface
Amount of force needed to pull the block

84. Frictional Forces of Different Surfaces
On which surface did you have to apply more force to move the block?