Download Lesson 2 Motion and Forces

Chapter 11 Lesson 2- Forces and Motion
Vocabulary
1. Force-
2. Friction-
3. balanced forces-
4. unbalanced forces-
5. action force-
6. reaction force-
NOTES
What are forces?
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Pushes, pulls, and lifts are all forces.
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Units of force are newtons (N) and pounds (lbs).
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Buoyancy lifts lighter substances out of denser substances.
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Thrust- push or pull of an airplane forward.
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Lift- causes the airplane to rise into the air.
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Lift must be stronger than the weight pulling on the plane in order for it to fly.
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Drag is a pull that slows the plane down.
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Forces can crush, stretch, or twist objects and deform them.
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The harder a substance is, the more force it takes to change its shape.
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A force can cause an object to start moving, speed up, change direction, slow down, or stop.
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Forces accelerate objects when they affect their motion.
What are gravity and friction?
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Gravity is the force that attracts all matter together.
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Newton's Law of Universal Gravitation
◦ Gravity depends on the masses of the objects and the distance between them.
◦ Increasing the mass increases the force, and increasing the distance decreases the force.

Friction makes it difficult to slide on rough surfaces.
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Smooth surfaces usually have less friction than rough surfaces.
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Friction increases when surfaces are pressed together with greater forces.
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Friction also increases with the weight of an object.
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Heat is created whenever there is friction.
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When an object moves through the air, the air hits the object and slows it down.
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Drag forces are a result of air resistance.
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Broad flat surfaces have the most drag.
What is Newton's First Law?

An object at rest tends to stay at rest, and an object in constant motion tends to stay in motion,
unless acted upon by an unbalanced force.
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Balanced forces do not cause motion.
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Unbalanced forces cause motion
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Newton’s 1st law is also called the Law of Inertia.
What is Newton's Second Law?

The unbalanced force on an object is equal to the mass of the object multiplied by its
acceleration: F= m X a.
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Using more rowers increases the force and increases acceleration.
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Having more passengers increases the mass and decreases acceleration.
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Acceleration increases as your force increases as long as your mass is not also changing.
What is Newton's Third Law?
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All forces occur in pairs, and these two forces are equal in strength and opposite in direction.
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For every action there is an opposite but equal reaction.
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Action and reaction forces are not balanced forces.
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When one object pushes on a second object, the second pushes back on the first with the same
strength.