Transcript Motion and Force

Chapter 11 Section 3
Physical Science (Freshman Physics)
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Define force
Explain the four fundamental forces
Describe the types of friction
Be able to state Newton’s first law of motion
Define inertia
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Force is defined as any action that can change
the state of motion of an object
Forces can act through contact or at a distance
There are four fundamental forces in nature:
1. Gravity – by far the weakest
2. Electromagnetic – Electricity and light
3. Weak nuclear – Keep electrons in motion
4. Strong nuclear – Holds protons and neutrons
together in the nucleus (Strongest)
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Forces that result from a push or a pull. Objects are
in contact with each other ~ hence the name contact
forces.
Examples:
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you catch a ball it stops
moving
You push a cart it starts
moving
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Do not require objects to be touching each other.
These forces can cause objects to move.
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Examples:
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gravity
magnets
magnets
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When two forces act equally and opposite, they
cancel out.
NO NET FORCE
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Unbalanced forces do not cancel completely.
The net force is greater than zero.
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The force of friction always opposes the motion.
It is always in the opposite direction of motion.
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The friction that occurs between two things that
are stationary.
Is greater than Kinetic friction.
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The force that opposes the movement of two
surfaces that are in contact and are moving over
each other.
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Sliding Friction – Objects are sliding
Rolling Friction – Objects are rolling
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Friction can be harmful or useful
First Semester
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British scientist and
mathematician
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One of the most prolific
scientists in history
1492
Christopher Columbus
stumbles upon an
already “discovered”
America
Gameboy first used in
1988
1642 - 1727
Isaac Newton
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Without an external force acting on it, an object
in motion will continue in motion.
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“An object at rest remains at rest and an object in
motion maintains its velocity unless it
experiences a net force
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Also known as “the law of Inertia”
An object
will just sit
there…
Unless…
A force is
applied
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The tendency of an object to resist a change in
motion unless an outside force acts on the
object.
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All objects resist change in motion, so all objects
have inertia.
• Objects
with greater mass have greater inertia.
More Inertia
Less Inertia
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When you travel in a car you have inertia.
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When the car brakes, turns or accelerates, you
experience an external force changing the
direction of your motion.
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Seatbelts provide the unbalanced force
necessary to stop you when your car stops.