Newton’s Contributions

• Calculus

• Light is composed of

rainbow colors

• Reflecting Telescope

• Laws of Motion

• Theory of Gravitation

NEWTON’S LAWS OFMOTION.

I. Newton’s first law (law of inertia)II. Newton’s second lawIII. Newton’s third law

Newton’s Laws of Motion

1st Law – An object at rest will stay at rest,

and an object in motion will stay in motion at constant velocity, unless acted upon by an unbalanced force.

2nd Law – Rate of change of momentum=

force applied.

3rd Law – For every action there is an equal

and opposite reaction.

Newton’s First Law

(law of inertia)

An object at rest tends to stay at rest and

an object in motion tends to stay in

motion unless acted upon by an external

unbalanced force.

Balanced Force

Equal forces in opposite

directions produce no motion

Unbalanced Forces

Unequal opposing forces

produce an unbalanced force

causing motion

Concept of Inertia:

“Inertia is the inherent property of all objects that they do not change their state of rest or of uniform motion along a straight line path unless acted upon by an external force.”

1st Law of Motion:

Unless acted

upon by an

unbalanced

force, this golf

ball would sit

on the tee

forever.

Newton’s 1st Law

Because of Inertia, objects resist changes in

their motion. When the car going 80 km/hour is stopped

by the brick wall, our body keeps moving at 80 m/hour.

Newton’s First Law (law of inertia)

MASS is the measure of the amount of matter in an object.

It is measured in Kilograms

Newton’s First Law (law of inertia)

INERTIA is a property of an object that describes how much it will resist the motion of the object.

more mass means more inertia .

If objects in motion tend to stay in motion,

why don’t moving objects keep moving forever?

Things don’t keep moving forever because there’s almost always an unbalanced force

acting upon them.

A book sliding across a table slows down and stops because of the force of friction.

If you throw a ball upwards it will

eventually slow down and fall

because of the force of gravity.

There are four main types of friction: Sliding friction: ice skating

Rolling friction: bowling

Fluid friction (air or liquid): air or water resistance

Static friction: initial friction when moving an object

The unbalanced force which opposes the motion of a moving body is ,

Frictional Force :

Slide a book across a table and watch it slide to a rest position. The book comes to a rest because of the presence of a force -that force being the

force of friction- which brings the book to a rest position.

In the absence of a force of friction, the book would continue in motion with the same speed and direction - forever! (Or at least to the end of the table top.)

Newton’s Second Law

Force equals mass times acceleration.

F = ma

2nd Law

Newton’s Second Law

• WEIGHT is a measure of the

force of ________ on the

mass of an object

• measured in __________

gravity

Newtons

Newton’s Second Law

One rock weighs 5 Newtons.

The other rock weighs 0.5

Newtons. How much more

force will be required to

accelerate the first rock

at the same rate as the

second rock?

Ten times as much

2nd Law

• When mass is in kilograms and

acceleration is in m/s/s, the unit of force is

in newtons (N).

• One newton is equal to the force required

to accelerate one kilogram of mass at one

meter/second/second.

If mass remains constant, doubling the acceleration, doubles the force. If force

remains constant, doubling the mass, halves the acceleration.

Linear Momentum:

Newton’s Third Law

For every action there is an equal and

opposite reaction.

Newton’s 3rd Law• For every action there is an equal and

opposite reaction.

Book to

earth

Table to

book

3rd Law

As the birds push down

on the air with their

wings, the air pushes

their wings up and

gives them lift, thus

obeying Newton’s 3rd

law of motion.

Action: earth pulls on you

Reaction: you pull on earth

Action and Reaction on Different Masses

Consider you and the earth

Action: tire pushes on roadReaction: road pushes on tire

3rd LawThe reaction of a rocket is an application of the third law of motion. Various fuels are burned in the engine, producing hot gases.

The hot gases push against the inside tube of the rocket and escape out the bottom of the tube. As the gases move downward, the rocket moves in the opposite direction.

ReviewNewton’s First Law:

Objects in motion tend to stay in motion and objects at rest tend to stay at rest unless acted upon by an unbalanced force.

Newton’s Second Law:

Force equals mass times acceleration (F = ma).

Newton’s Third Law:

For every action there is an equal and

opposite reaction.