Transcript Cool Dudes of Science!

The Science of Motion
Cool Dudes of Science!
Aristotle
From the Louvre
Aristotle
Lived from 384-322 BCE (Greek)
 Used logic to theorize that things fell to
earth so therefore the earth was the
center of the universe
 Falling objects fell at a speed
proportional to their weight
 Ideas shaped scientific thought for 2000
years!
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Copernicus
Copernicus
Lived 1473-1543
 Using careful observations and math, he
reasoned that the earth moved around
the sun
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Galilieo Galilei
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Considered the “father of science”
“All truths are easy to understand once
They are discovered; the point is to
discover them.”
Galileo
Lived 1546-1642
 First to prove that Aristotle was wrong
about falling objects
 He dropped 2 cannon balls from the
Leaning Tower of Pisa, one 10x heavier
than the other. What would Aristotle
have predicted?
 The two balls hit at the same time!!
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Falling Objects
If Galileo was right, why don’t sheets of
paper and paper clips hit the ground at
the same time?
 Air resistance will slow objects down.
In the absence of an atmosphere all
objects, regardless of mass, will fall at
the same rate.
 hammer and feather on the moon
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Sir Isaac Newton
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Newton’s Laws
Newton
Lived from 1642-1727
 Came up with universal law of
gravitation
 Came up with laws of motion
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Gravity
Universal Law of Gravitation: The force of
gravity acts between all objects in the
universe
 Strength of force depends on:
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Mass - the bigger the object’s mass, the more
force or pull it produces
Distance- the closer together, the bigger the pull.
F= (mass of object 1 x mass of object 2) / r2
where r=the distance between the objects
Gravity
Gravity is an attractive force
 Acceleration due to gravity is 9.8m/s2
 Air resistance is friction with the air, it
opposes gravity
 Mass – the amount of matter in an
object
 Weight- the measure of the force of
gravity on an object
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Terminal Velocity!
The maximum velocity a falling object can achieve.
The air resistance equals the force of gravity so the
object does not accelerate any more.
http://hypertextbook.com/facts/JianHuang.shtml
1st Law of Motion- Inertia
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An object at rest stays at rest, an object
in motion stays in motion, unless an
outside force acts upon it.
2nd Law of Motion F=ma
The net force on an object is equal to
the product of its mass and acceleration
 Force = mass x acceleration
 m1 x
a1
=
m2 x
a2
(big) (little) = (little)
(big)
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3rd Law of Motion = & opposite
For every action there is an equal and
opposite reaction
 Example: When you let a balloon go,
the air rushing out the end forces the
balloon in the opposite direction. The
greater the rush of air, the faster the
balloon moves
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Friction & Force
Force: a push or a pull that is exerted
on an object and gives the object
energy to start moving, or change
direction.
 Friction: A force that opposes the
motion of an object.
 Types: sliding, rolling, fluid
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Friction
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Which object below encounters more
friction? Why?
Measuring Force
One unit used to measure force is called
the Newton
 A Newton (N) is defined as the metric
unit of force needed to move a 1 kg
mass 1 m in 1 second
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