Newton

1
Newtons Laws of Motion

• I. Inertia
• II. Fma
• III. Action-Reaction Forces

2
Isaac Newton

• Sir Isaac Newton
• 1642 1727
• Scientist and Mathematician
• He defined the laws of motion and universal
  gravitation, which he used to predict precisely
  the motions of stars, and the planets around the
  sun. He published the laws in his book
  Philosophiae Naturalis Principia Mathematica
  (Mathematic Principles of Natural Philosophy) in
  1687.

If I have ever made any valuable discoveries, it
has been owing more to patient attention, than to
any other talent. Sir Isaac Newton
3
Four Forces

• Electromotive (EMF) Magnetism
• Gravity Friction/Air Resistance

4
But there are more.

•  
• Applied The force an object exerts on another
  object.
•  
• Spring The force of a spring pushing or
  pulling on an object.
•  
• Tension- The force a rope or cord puts on an
  object
•  
• Normal The force a surface applies upward
• on an object
•  
•  

5
Forces and Newtons Laws

• Newtons three laws of motion affect all these
  forces.

6

• While most people know what Newton's laws say,
  many people do not know what they mean (or simply
  do not believe what they mean).

7
Metric Force

• A force is a push or a pull.
• The metric unit of force is the Newton (N), named
  after Sir Isaac Newton.
• It is equal to 1 kg-m/s/s.
• It is a force of about ¼ a pound like a stick
  of butter.

8
What is meant by a balanced force?
If the forces on an object are equal and
opposite, they are said to be balanced, and the
object experiences no change in motion.
9
What is meant by an unbalanced force?

• If they are not equal and opposite, then the
  forces are unbalanced and the motion of the
  object changes.

10
First Law of Motion

• The first law of motion states If no net force
  acts on it
• an object at rest remains at rest and
• an object in motion remains in motion in a
  straight line at a constant velocity
• It will keep on
• keepinon

11
Newtons 3 Laws of Motion

• Newtons 1st Law of Motion
• AKA The Law of Inertia

Remember The greater the mass of an object the
greater the inertia
12
Newtons First Law is also called the Law of
Inertia

• Inertia the tendency of an object to resist
  changes in its state of motion
• The First Law states that all objects have
  inertia. The more mass an object has, the more
  inertia it has (and the harder it is to change
  its motion).

13
1st Law

• Inertia is the tendency of an object to resist
  changes in its velocity - whether in motion or
  motionless.

These pumpkins will not move unless acted on by
an unbalanced force.
14
What does this mean?

• This means that there is a natural tendency of
  objects to keep on doing what they're doing.

15
Examples

• Soccer
• If I kick a soccer ball towards the net and the
  goalie is not there to stop it
• GOAL!!!

• Bowling
• When I roll the ball
• down the lane, it will
• keep going until it hits
• the pins or the gutter!

16
Example

• Two teams are
• playing tug of
• war. They are
• both exerting
• equal force on
• the rope in
• opposite
• directions. This
• balanced force
• results in no
• change of motion.

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Example
A powerful locomotive begins to pull a long line
of boxcars that were sitting at rest. Since the
boxcars are so massive, they have a great deal
of inertia and it takes a large force to change
their motion. Once they are moving, it takes a
large force to stop them.
18
Foucault Pendulum
On the top right is the Foucault Pendulum at the
Pantheon in Paris, France. http//www.youtube.com/
watch?vnB2SXLYwKkMsafety_modetruepersist_safet
y_mode1 Inertia keeps a pendulum swinging in
the same direction regardless of the motion of
the earth. This can be used to measure the
motion of the earth. As the Foucault Pendulum
swings it appears to be rotating, but it is the
earth that is rotating under it.
http//www.calacademy.org/products/pendulum/
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• Unless acted on by
• an unbalanced
• force (such as a golf
• club or the wind) the
• ball would sit on the
• tee forever!

20

• Unless acted on by an unbalanced force such as
  gravity and air resistance (fluid friction),
  once airborne,
• the ball would never stop!

21
Why?

• Why then, do we observe every day objects in
  motion slowing down and becoming motionless
  seemingly without an outside force?
• Its forces we cannot see

22
Things dont keep moving forever because theres
almost always an unbalanced force acting upon it.
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.
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In outer space, away from gravity and any sources
of friction, a rocket ship launched with a
certain speed and direction would keep going in
that same direction and at that same speed
forever.
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Newtonss 1st Law and You
Because of inertia, objects (including you)
resist changes in their motion. When the car
going 65 m/hour is stopped by the brick wall,
your body keeps moving at 65 m/hour. Dont let
this be you. Wear a seat belt!
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How does Newtons 1st Law Relate to Your Life?

• Transporting something in the bed of a truck
  http//www.youtube.com/watch?vYlQXnXIqka0
• Think about riding a bike
• http//www.youtube.com/watch?vYmgxrzpKH4A
• (Dont try this at homeduh) Think about riding
  ON a car
• http//www.youtube.com/watch?v-QqAcHDvSjY
• Riding a motorcycle
• http//www.youtube.com/watch?v5pt86fpS57c
• Wearing seatbelts
• http//www.youtube.com/watch?vs09dy2a7omI
• Expensive OUCH!
• http//www.youtube.com/watch?vpxewzpVPgAE