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Newton’s Three Laws of Motion

Newton's laws of

motion are three physical

laws which provide

relationships between the

forces acting on a body

and the motion of the

body.

Sir Isaac Newton (January 1643 – March 1727)

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An object at rest

will remain at

rest- unless acted

upon by an

outside force.

Newton’s First Law of Motion

An object in

motion will remain

in motion – unless

acted upon by an

outside force.

Newton’s First Law of Motion

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An object at rest remains at

rest, and an object in

motion remains in motion at

a constant speed and in a

straight line unless acted

on by an unbalanced force.

Newton’s First Law of Motion

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Newton’s First Law of Motion

Inertia is a resistance to

change in motion.

Newton’s First Law of Motion AKA The Law of Inertia

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Can You Explain…Newton’s First Law of Motion

An object at

rest will

remain at

rest…

DemosNewton’s First Law of Motion

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Table Cloth TrickNewton’s First Law of Motion

Can You Explain…Newton’s First Law of MotionAn object in motion will

continue to move in a

straight line.

For Example…

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The Story of FluffyNewton’s First Law of Motion

Poor Baby BarbieNewton’s First Law of Motion

http://www.physicsclassroom.com/mmedia/newtlaw

s/cci.cfm

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Anti-Inertia BeltsNewton’s First Law of Motion

Better known

as “Seatbelts” !

The acceleration of an object depends on the

mass of the object and the amount of force

applied.

• Newton’s second law describes the motion

of an object when an unbalanced force acts

on the object.

Newton’s 2nd Law of Motion

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Newton’s 2nd Law of MotionThis Law shows the

relationship between

mass, force, and

acceleration.

When a force is

applied to a mass, it

accelerates.

The larger the mass of an

object, the more force needed

to start it, stop it, or change its

direction.

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A speeding bullet and a slow moving train

both have tremendous force. The force of

the bullet can be attributed to its incredible

acceleration while the force of the train

comes from its great mass.

Newton’s 2nd Law of MotionForce = mass x acceleration

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The acceleration of an object depends on the mass of

the object and the amount of force applied.

• Newton’s second law describes the motion of an

object when an unbalanced force acts on the object.

Newton’s 2nd Law of Motion

• Part 1: Acceleration Depends on Mass The

acceleration of an object decreases as its mass

increases. Its acceleration increases as its mass

decreases.

• Part 2: Acceleration Depends on Force An object’s

acceleration increases as the force on the object

increases. The acceleration of an object is always in

the same direction as the force applied.

Newton’s 2nd Law of Motion

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Newton’s 2nd Law of Motion

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Newton’s 2nd Law of Motion

Newton’s 2nd Law of Motion

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For Example:

A Bowling Ball vs a

ping pong ball.

Newton’s 2nd Law of Motion

Or Runaway Ramps

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Choose Your Position..

Some Athletes arelong and lean, with

little body fat, and

little muscle.

Basketball players

and wide receivers

fit this category.

Choose Your Position…

Other athletes, on

the other hand, have

lots of body fat, lots

of muscle, and gain

weight easily.

Football lineman

and sumo wrestlers

are heavier and

rounder individuals

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Momentum, Mass, and Velocity

• The momentum of an object is the product of the

object’s mass and velocity. Object at rest has zero

momentum.

Calculating Momentum The relationship of

momentum (p), mass (m) in kilograms, and velocity (v)

in meters per second, is shown in the equation below:

p m x v

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What is (i) the total kinetic energy before the collision;

(ii) the total kinetic energy after the collision.

(iii) the total loss in kinetic energy.

Momentum

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Momentum

• The law of conservation of momentum states that any

time objects collide, the total amount of momentum

stays the same.

Law of Conservation of Momentum

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• The combined objects have a different velocity

because momentum is conserved and depends

on mass and velocity.

• So, when the mass changes, the velocity must

change, too.

Law of Conservation of Momentum

• Objects Bouncing Off Each Other

When two objects bounce off each other,

momentum is transferred from one object to

the other.

• The transfer of momentum causes the

objects to move in different directions at

different speeds.

Law of Conservation of Momentum

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Because action and reaction

forces are equal and opposite,

momentum is neither gained or

lost in a collision.

Law of Conservation of Momentum& Newton’s 3rd Law can be

explained…

Forces Always Come in Pairs

.

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Newton’s Third Law of Motion

Whenever one object exerts a force on a second

object, the second object exerts an equal and opposite

force on the first.

• Newton’s third law of motion can be simply stated as

follows: All forces act in pairs.

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For every action force,

there is an equal, but

opposite, reaction

force.

Newton’s 3rd Law of Motion

The Action Force is Equal in

size but Opposite in Direction.

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Action and Reaction forces

always act on different

objects.

Action Force: The man

pushes against the

wall.

Reaction Force: the wall

pushes on the man.

Newton's third law does not mean that forces always cancel out

so that nothing can ever move. If these two figure skaters,

initially at rest, push against each other, they will both move.

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Another example: Recoil of a

gun or cannon

Or…Launching a Rocket

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Or… a Lawn Sprinkler