Download Newtons Laws

Newton’s Laws
Solar System
Galileo & Copernicus
explained:
The Sun was in the
center of the solar
system

Kepler explained:
• Planets have elliptical
orbits around the Sun
• Planets orbit at different
speeds.
• Planets cover equal area
in equal time.
• The farther the distance
from the Sun, the greater
the orbital period.
2
Isaac Newton (1642 – 1727)



One of the most brilliant
theoreticians to ever live.
WHY
Explained
the
planets move as they do.
He formulated three laws of
motion and the law of universal
gravitation.
3
Terms to describe motion


FORCE:
A push or pull
that changes the
motion of an
object


VELOCITY:
Describes how
fast (speed) an
object moves in
a direction
4
Newton’s 1st Law of Inertia:
Objects in uniform straight line motion continue in straight
line motion unless an outside force is applied to change their
motion
Once in orbit, a planet
will CONTINUE its orbital
motion at constant
velocity until an outside
force (asteroid, another planet?)
acts on it to change its
orbit.
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Gravity

Gravity: a FORCE that pulls every
mass toward every other mass
– Since Earth is the largest mass around –
gravity pulls everything toward the center
of Earth
You have mass. Are you gravitationally
attracted to the person sitting next to you?
Gravity is Universal
Newton’s Third Law
“To every action there is an equal and opposite re-action.”
Whenever one object exerts a force on a second object,
the second object exerts an
equal and opposite force on the first object.
Forces are interacting in PAIRS
– one object on another
Mass
#1
Mass
#2
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• Gravity is the way that masses communicate
with each other!
• Every mass in the universe is attracted to every
other mass.
I’m
attracted
to you
more!
I feel
your
force of
attraction
2 kg
1 kg
Gravity is related to Mass
• The more mass an object, the more gravity!!
• Which planet has more gravitational pull?
VS
“center’ of gravity
• There are A LOT of particles in an
object
– We say that the force on an object acts
as though all the mass was concentrated
at the CENTER of the object.
– Example:
d
Law of Universal Gravity
Mass attracts mass
14
Newton’s Law of Gravity
Formula?
Mass of one object
Mass of a second object
Fg = Gm1x m2
d2
squared
Distance between them
Big “G” is a constant (a multiplier)
It’s the ‘amount’ of force of attraction between two bodies each with a
mass of 1 kilogram
1 meter
6.67 x 10-11 N*m2/kg2 or
.0000000000667
Rotate around the room to find masses and distances for complete the table
F=G(M1*M2)/d2 NOTE: We are ignoring G for this exercise (make it =1); G is just a constant
Trial
Mass 1
(kg)
Mass 2
(kg)
M1xM2
(kg2)
Distance Distance2 Force of
(m)
(m2)
Gravity (N)
1
2
3
4
5
6
17
Calculate the force of gravity by dividing the masses by the distance2
F=G(M1*M2)/d2 NOTE: We are ignoring G for this exercise (make it =1); G is just a constant
Trial
Mass 1
(kg)
Mass 2
(kg)
M1xM2
(kg2)
Distance Distance22 Force of
(m)
(m2)
Gravity (N)
1
2
3
4
5
6
18
1 kg
2 kg
1 kg
2 kg
19
1
2
4
8
16
64
MASS x MASS kg
20
Force of gravitational pull
Distance and Gravity
Does gravity get more, less,
stay the same as you go
further DISTANCE from
earth?
1 kg
2 kg
1 kg
2 kg
22
ESS Unit 3
Name ______________________ Period ________
Using the diagram above, make a graph of your Distance vs. force of gravity below:
Predicted trend for Distance vs. Gravity
1.0 N
Force of gravity
If distance between objects increases,
Then the force of gravity will decrease
.50 N
.25 N
.125 N
.06 N
.03 N
1d
2d
3d
(D)2
meters
4d
5d
6d
23
The mass of the planet and the satellite are constant. Fill-in the force of gravity at each distance
1d
2d
3d
Fg=_1m__
12
Fg=1m_
22
11
________N
1/4
__________N
________N
Fg=_1m_
32
4d
Fg=_1m_
42
_________N
5d
Fg=_1m_
52
_________N
6d
Fg=_1m_
62
_________N
(.25)
24
ESS Unit 3
Name ______________________ Period ________
Using the diagram above, make a graph of your Distance vs. force of gravity below:
1.0 N
Distance vs. gravity
1
0.9
Force of Gravity
Force of gravity
0.8
0.7
0.6 .50 N
0.5
0.4
.25 N
0.3
.125 N
0.2 .06 N
.03 N
0.1
1d
2d
3d
4d
5d
6d
0
1
2
3
2
(D)
4
distance
meters
5
6
25
According to Newton’s Law of Gravity,
Can the orbiting space station get away from the
Earth’s gravity? Is there such a thing as “zero” g?
◦
◦

NO!
Then why do the astronauts appear to be floating?
What would happen to the space station is it
was free from Earth’s gravity?
If the Earth’s gravity force is attracting the moon,
Then Why doesn’t the moon get pulled into Earth?
The moon has
VELOCITY!
It’s moving with a
constant speed in a
direction – straight.
As long as the FORCE of gravity toward Earth is EQUAL to
the forward motion of velocity of the moon it will ORBIT
PHET on Orbits Bell work
1.
2.
3.
4.
5.
The force of gravity (pulls, pushes) masses.
The more mass, the ____ gravitational pull.
The more distance, the ________ the
gravitational pull.
What 2 forces keep an object in motion:
Diagram what would happen to an orbiting
planet if:
1.
2.
3.
gravity was turned OFF
The planet slowed down in orbit (decreased velocity)
The planet increased its speed (velocity)
Gravity Facts
1.
2.
3.
4.
5.
Attractive force between all objects with
mass
Universal – everything with mass has it and
is affected by it
Mass & gravity = directly proportional
m↑, g↑
Distance & gravity = inversely proportional
d↑, g↓
Attractive force is from centers of objects
NEVER be zero