Transcript Forces and Newton

Forces and Newton
Forces
A Force is a push
or a pull.
 Examples
include
 Gravity
 Contact
Force
 Friction
 Magnetic
force
 Electrical force
Forces can be
Balanced or
Unbalanced
Which side will win?????
Video Clips

Play Push and Pull clip – 3:14
(You may need to log into United Streaming)
Balanced Forces
do NOT change the object’s
motion
Unbalanced Forces
cause objects to
Start moving
 Stop moving
 Change direction

Unbalanced Forces
When in the
opposite
direction, the
box moves the
direction of
the larger
force.
WORK
The
amount of force used to
move an object.
Work is done anytime force causes an object to
move.
Work is not done when there is no motion.
Quiz

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A push or pull is called a
______
When two equal forces are
acting on an object in opposite
directions they are _________
forces
When forces are unequal they
are _________ forces.
Forces are described in strength
and ________
A.
B.
C.
D.
Force
Direction
Balanced
Unbalanced
Sir Isaac Newton (1642 - 1727)
His ideas are built upon the
ideas of Galileo. Newton's
three Laws of Motion are
general, universal LAWS
that explain a wide range of
situations. (Newton also
invented Calculus and the
reflecting telescope).
1st Law of Motion
(Law of Inertia)
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.
st
1
Law
 Inertia
is the
tendency of an
object to resist
changes in its
velocity:
whether in
motion or
These pumpkins will not
move unless acted on by
motionless.
an unbalanced force.
The car hits the wall and stops, but the
person keeps on going because he is
not part of the car.
How can the person become part of the
car?
Video Clips
Play Newton’s 1st Law of Motion clip (2:13)
(United Streaming)

Newton’s Ideas Continued

Newton’s second law shows how force, mass, and
acceleration link together.

The 2nd law shows that both the size of the force and
the mass of the object affect the object’s acceleration.

Force is measured in a unit Newton (N).
nd
2
Law
nd
2
Law
F = Force
m = Mass
a = Acceleration
nd
2
Law (F = m x a)

How much force is needed to accelerate a 1400
kilogram car 2 meters per second/ second?
Write the formula
F=mxa
Fill in given numbers and units
F = 1400 kg x 2 meters per second/second
Solve for the unknown

2800 kg-meters/second/second or 2800
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N
nd
2
Law
Click below to learn more.

http://www.youtube.com/watch?v=UhCG0qo
Y9Dc
Newton’s Ideas Continued
 Newton’s
Third Law is often
called the action-reaction in action
law.
rd
3
 For
Law
every action, there is an
equal and opposite reaction.
Newton’s 3rd Law in Nature

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Consider the propulsion of a
fish through the water. A fish
uses its fins to push water
backwards. In turn, the
water reacts by pushing the
fish forwards, propelling the
fish through the water.
The size of the force on the
water equals the size of the
force on the fish; the
direction of the force on the
water (backwards) is opposite
the direction of the force on
the fish (forwards).
rd
3
Law
Flying gracefully
through the air, birds
depend on Newton’s
third law of motion. As
the bird pushes down
on the air with their
wings, the air pushes
their wings up and
gives them lift.
3rd Law
The 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.
Review
3 Laws of Motion
http://www.youtube.com/watch?v=iH
48Lc7wq0U