​Friction and Gravity

Chapter 10, Lesson 3​

Pages 378-385

What Factors Affect Friction?

Friction - the force that two surfaces exert on each other when they rub against each other

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Two factors that affect the force of friction are the types of surfaces involved and how hard the surfaces are pushed together

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Smooth surfaces produce less friction than rough surfaces​

What Factors Affect Friction?

If you rubbed your hands together forcefully, there would be more friction than if you rubbed them together lightly

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Friction increases when surfaces push harder against each other

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Friction acts in the opposite direction of the object's motion - without friction a moving object will not stop until it hits another object​

Types of Friction - Page 380-381

Sliding Friction - when two solid surfaces slide over each other

​Static Friction - friction that acts between two objects that are not moving

Fluid Friction - when a solid object moves through a fluid​ (any substance that can easily flow)

Rolling Friction - when an object rolls across a surface​

Label five examples of each type of friction on the picture in your book​

What Factors Affect Gravity?

Gravity - force that can act at a distance to pull object toward each other

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Gravity acts EVERYWHERE in the universe - it is the force that keeps all of the planets in our solar system orbiting around the sun

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The Law of Universal Gravitation states that the force of gravity acts between all objects in the universe that have mass​

Factors Affecting Gravity

A gravitational force acts between any two objects in the universe, but it is stronger in some directions than in other directions

​Two factors affect the gravitational attraction between objects: mass and distance

​Mass - a measure of the amount of matter in an object

Gravitational forces change as the mass or distance between objects changes - the more massive an object, the stronger it's gravitational forces; the closer the objects, the stronger their gravitational forces​

Weight and Mass

Mass is often confused with weight

Weight - a measure of the force of gravity on an object

Your mass would not change if you were on the moon but your weight (the amount of gravitational force acting on you) would​