Download Chapter 11 Lesson 2- Forces and Motion Vocabulary force friction

Chapter 11 Lesson 2- Forces and Motion
Vocabulary
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force
friction
balanced forces
unbalanced forces
action force
reaction force
NOTES
What are forces?
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Pushes, pulls, and lifts are all forces.
Units of force are newtons (N) and pounds (lbs).
Buoyancy lifts lighter substances out of denser substances.
Thrust- push or pull of an airplane forward.
Lift- causes the airplane to rise into the air.
Lift must be stronger than the weight pulling on the plane in order for it to fly.
Drag is a pull that slows the plane down.
Forces can crush, stretch, or twist objects and deform them.
The harder a substance is, the more force it takes to change its shape.
A force can cause an object to start moving, speed up, change direction, slow down, or stop.
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.
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.
Smooth surfaces usually have less friction than rough surfaces.
Friction increases when surfaces are pressed together with greater forces.
Friction also increases with the weight of an object.
Heat is created whenever there is friction.
When an object moves through the air, the air hits the object and slows it down.
Drag forces are a result of air resistance.
Broad flat surfaces have the most drag.
What is Newton's First Law?
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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.
Balanced forces do not cause motion.
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Unbalanced forces cause motion
Newtons 1st law is also called the Law of Inertia.
What is Newton's Second Law?
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The unbalanced force on an object is equal to the mass of the object multiplied by its
acceleration: F= m X a.
Using more rowers increases the force and increases acceleration.
Having more passengers increases the mass and decreases acceleration.
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.
For every action there is an opposite but equal reaction.
Action and reaction forces are not balanced forces.
When one object pushes on a second object, the second pushes back on the first with the same
strength.