Forces Contact vs. Noncontact

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?

Agenda Bell Ringer PowerPoint with Notes Brain Pop with Review Quiz: Gravity Check for Understandings Mini Book Activity Independent Practice

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

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.

What force is seen in these pictures A man lifting weights A book on a table Children sliding Flying a kit

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: Noncontact 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.

What force is seen in these pictures

Gravity Mass and distance affect the force of gravity. The greater the mass and the closer the object, the stronger its gravitational pull.

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.

Mass vs. Weight The amount of matter in an object. Unit: Grams Does not depend of 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.

BRAIN POP: Gravity Quiz Afterwards!

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.

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 http://www.youtube.com/watch?v=WaP3vXiioJk&safe=active 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.

Independent Practice