Transcript Newton’s Laws of Motion

Motion &
Newton’s Laws
Earth Systems
A force
a
push
or
a
pull.
is…
Friction, Drag, Gravity, and Weight are
forces.
Measured in unit N = kg m
sec2
Background Knowledge
continued. . .
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Sir Isaac Newton is famous for explaining
the motion of object using mathematics.
SPEED: a measurement of distance
traveled in a given time.
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Speed = distance
time
Units: m/sec
VELOCITY: an objects speed and direction.
Background Knowledge
continued.. .
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ACCELERATION: Change in velocity
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Increase in velocity: acceleration
Decrease in velocity: deceleration or negative acceleration.
Acceleration: final velocity – initial velocity
time
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Units:
m
sec2
Graphing
If Sally got to school on foot
and bus describe her
movement according to the
graph.
•Sally walked to the bus
stop at .5 km/min
•She sat waiting for the bus
0 km/min
•She rode the bus at a
average speed of
Acceleration “dot diagram”
Dot represents an object’s position at different times.
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Acceleration: distance increases each second
1 sec
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3 sec
5 sec
7 sec
Negative Acceleration / deceleration: distance
decreases each second
1 sec
3 sec
5 sec
7 sec
video
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http://videos.howstuffworks.com/discovery/2
9421-assignment-discovery-newtons-lawsof-motion-video.htm
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Assignment Discovery: Isaac Newton’s Principia
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Exploring the laws of motion: Newton’s 1st law
Lego video:
http://www.youtube.com/watch?v=NWE_aG
qfUDs
1st Law: The Law of Inertia
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An object in motion will stay in motion,
An object at rest will stay at rest,
unless an outside force acts on it.
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Newton’s 1st Law rap
http://www.youtube.com/watch?v=OaKc4PlrEY8
Larger mass larger inertia
Smaller mass smaller inertia
Example:
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Table cloth trick
Penny in a flask
Dinosaur riding on hood of car
1st law stated again
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If no unbalanced force acts on an
object the object will continue moving
at the same speed in the same
direction
If an object is not moving and at rest
the object will remain at rest until an
outside force acts upon it.
Friction and gravity are the
unbalanced forces that are acting on
all the motion that we observe.
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Friction is the force that slows things
down when two objects rub together.
Friction slows objects until they stop,
heats things up and wears them down.
Gravity is the force pulling two objects
together
Newton’s 1st Law and You
Don’t let this be you. Wear seat belts.
Because of inertia, objects (including you) resist changes
in their motion. When the car going 80 m/hour is stopped
by the brick wall, your body keeps moving at 80 m/hour.
Inertia = Mass
Bigger masses have more…
Smaller masses have less inertia.
Inertia = Resistance to…
changing speed.
changing direction.
Inertia = resistance to changes in
motion.
Large masses
resist net forces
and do not
accelerate much.
A large mass resists changing
its velocity.
What if we put rockets on each
creature?
Small masses change
motion easily.
Large masses resist
changing motion.
2nd Law
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Force = mass x acceleration
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Animations: \http://videos.howstuffworks.com/discovery/29421-assignment-discovery-newtons-laws-ofmotion-video.htm
http://www.youtube.com/watch?v=7_fbH-muvlw&feature=related “Three laws of motion”
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Assignment Discovery: Newton’s Laws of Motion
(http://videos.howstuffworks.com/discovery/29421-assignment-discovery-newtons-laws-of-motionvideo.htm) show for 2nd law
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2nd Law
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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.
2nd Law (F = m x a)
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How much force is needed to
accelerate a 1400 kilogram car 2
meters per second/per 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
3rd Law
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For every action, there is
an equal and opposite
reaction.
3rd Law
According to Newton,
whenever objects A
and B interact with
each other, they
exert forces upon
each other. When
you sit in your chair,
your body exerts a
downward force on
the chair and the
chair exerts an
upward force on your
3rd Law
There are two forces
resulting from this
interaction - a force
on the chair and a
force on your body.
These two forces are
called action and
reaction forces.
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
3rd Law
Flying gracefully
through the air, birds
depend on Newton’s
third law of motion. As
the birds push down on
the air with their wings,
the air pushes their
wings up and gives
them lift.
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Consider the flying motion of birds. A bird
flies by use of its wings. The wings of a bird
push air downwards. In turn, the air reacts
by pushing the bird upwards.
The size of the force on the air equals the
size of the force on the bird; the direction of
the force on the air (downwards) is opposite
the direction of the force on the bird
(upwards).
Action-reaction force pairs make it possible
for birds to fly.
Other examples of Newton’s
Third Law
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The baseball forces
the bat to the left
(an action); the bat
forces the ball to
the right (the
reaction).
3rd Law
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Consider the
motion of a car on
the way to school.
A car is equipped
with wheels which
spin backwards. As
the wheels spin
backwards, they
grip the road and
push the road
backwards.
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.
Non newtonian fluid
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Non newtonian fluid pool
http://www.youtube.com/watch?v=f2X
Q97XHjVw