1. Forces Contact vs. Noncontact
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2. Objectives Essential Question
Distinguish between contact and noncontact forces.
Explore the Law of Gravity by recognizing that every object exerts a gravitational force.
Essential Question
What forces may hinder the motion of a soccer ball rolling across a field?
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3. Agenda Bell Ringer PowerPoint with Notes
Brain Pop with Review Quiz: Gravity
Check for Understandings
Mini Book Activity
Independent Practice
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4. Force: A push or Pull Contact Force Non-Contact Force
A force that can cause or change motion of an object by touching it. Motors and gears operate through contact forces.
Force that results when the two objects are not in physical contact with each other, yet are able to exert a push or pull.
Contact Force Examples:
Friction
Normal Force
Air Resistance
Applied Force
Non-Contact Force Examples:
Gravitational Force
Electrical Force
Magnetic Force
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5. Contact Forces
Applied Force: A force typical push or pull, pushing a door open, pulling a rope.
Friction: Happens when two objects rub against each other. Friction opposes motion.
Normal Force: The normal force is the support force exerted upon an object that is in contact with another stable object. For example, if a book is resting upon a surface, then the surface is exerting an upward force upon the book in order to support the weight of the book.
Air Resistance: The air resistance is a type of frictional force that acts upon objects as they travel through the air.
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6. Contact Forces Gravity Cyclist movement Air resistance Friction
Image credits:
Cyclist Laura Brown by Flickr user Flowizm, (CC BY-NC-SA 2.0)
Military skydiver by Pixabay user skeeze, (CC0 Public Domain)
Friction
Normal force = 10N
Weight = 10N
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7. NON-Contact Forces
Magnetic Force: A kind of non-contact force; materials such as iron, nickel, cobalt and other magnets just need to be near the magnet to be attracted or repelled.
Electric Force: Non-contact force of electrical charges.
Gravitational Force: The force of attraction between any two objects in the universe. All objects have gravitational force. The mass of an object and its distance determines the strength of its gravitational force.
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8. Gravity
Mass and distance affect the force of gravity. The greater the mass and the closer the object, the stronger its gravitational pull.
Image credits:
Human silhouettes walking on globe, Pixabay user geralt, (CC0 Public Domain)
Gravity Probe B and Space-Time, artist’s conception from NASA, (public domain; government publication)
Newton under the apple tree by Frits Ahlefeldt, (CC BY-NC-ND 2.0)
“What is Weight,” NASA, (public domain; government publication)
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9. Gravity
How does the force of gravity change as the mass of objects and distance between them changes?
The force of gravity between two objects depends on two factors:
Mass
Distance
*Longer arrows represent a greater force of gravity.
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10. Mass vs. Weight The amount of matter in an object. Unit: Grams
Does not depend on gravity.
Measured with a triple beam or digital balance.
Measure of the Earth’s gravitational pull (a force).
measured in lbs. or N
Changes depending on the gravitational force.
Measured using a spring scale.
Image credits:
Triple beam balance, by Flikr user biologycorner, (CC BY-NC 2.0)
Spring scale, (public domain)
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11. Classify the Forces A foot kicking a soccer ball
An apple falling off a tree
A paper clip sliding towards a magnet
A bat striking a baseball
Two magnets pushing apart from one another
The moon orbiting the Earth
A compass needle turning North
A hand pushing an object
Shoes rubbing against the floor
Have students specify contact or non- contact as well as specific type of force. For example: A foot kicking a soccer ball is a contact force: applied force.
Answers:
1. Applied
2. Gravity
3. Magnetic
4. Applied
5. Magnetic
6. Gravity
7. Magnetic
8. Applied
9. Friction
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12. Discuss! Essential Question
Now that we have learned about forces, let’s talk about the essential question! You will answer the EQ on the front of your foldable.
Essential Question
What forces may hinder the motion of a soccer ball rolling across a field?
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13. Make a Book!
Time to tap into some creativity! You will create a 6-page book that covers what you learned today.
(10 minutes)
Front Cover: “Force: A Push or Pull”
Your name and the period.
Page 1: Contact Force
Page 2: Examples
Page 3: Non Contact Force
Page 4: Examples
Page 5: Gravity
Page 6: Summary
Teacher notes: Have students summarize the definition in their own words on pages 1, 3, and 5. On page 2 and 4 they should provide examples of these type of forces that were NOT used in the presentation.
Image credit:
Book, (CC BY-SA 3.0)
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14. Independent Practice Image credit:
The clock face of Big Bin (Elizabeth Tower), (CC BY-SA 4.0)
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