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Friction and Gravity (Friction (The Causes of Friction (The strength of…
Friction and Gravity
Friction
The Causes of Friction
The strength of the force of friction depends on 2 factors: how hard the surfaces push together and the types of surfaces involved.
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Without friction, a moving object might not stop until it strikes another object.
Static Friction
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Because of static friction, you must use extra force to start the motion of stationary objects.
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Rolling Friction
When an object rolls across a surface, rolling friction occurs.
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Rolling friction is the type of friction that is important to engineers who design certain materials.
Fluid Friction
Fluids, such as water, oil, or air, are materials that flow easily.
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Like rolling friction, fluid friction is easier to overcome than sliding friction.
Gravity
Universal Gravitation
Newton realized that gravity acts everywhere in the universe, not just on Earth.
It is the force that keeps the moon orbiting around earth, makes an apple fall to the ground, that keeps all the planets in our solar system orbiting around the sun.
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Weight and Mass
Mass is a measure of the amount of matter in an object; weight is a measure of the gravitational force exerted on an object.
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Gravity and Motion
Free Fall
When the only force acting on a falling object is gravity, the object is said to be in free fall.
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In free fall, the force of gravity is an unbalanced force that causes an object to accelerate.
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Air Resistance
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You can see the effect of air resistance if you drop a flat piece of paper and a crumpled piece of paper at the same time.
Since the flat paper has a greater surface area, it experiences greater air resistance falls more slowly.
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As a falling object speeds up, the force of air resistance becomes greater and greater.
As a falling object speeds up, the force of air resistance becomes greater and greater.
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