Transcript Newton`s Laws of Motion

Newton’s Laws of Motion
The First Law
“An object at rest tends to stay at rest,
and an object in motion tends to stay in
motion (straight line, constant velocity)
unless acted on by outside force.”
In the Solar System that outside force is
usually gravity.
Why we need seat belts…
If you break the Seat Belt Law, you
might be obeying Newton’s First Law!
The Moon tries
to “obey” the
First Law, but
the Earth’s
gravitational
pull forces it
into an elliptical
orbit.
Concept of Escape Velocity
• If a cannon is fired
from a high
mountain, it will
eventually be
brought down to
Earth.
• Given more velocity
it will encircle the
Earth.
If more velocity is given…
• The orbit will
increase its
altitude, becoming
elliptical.
• When a speed of
around 18 mps is
reached, the
cannonball
escapes.
Newton’s Cannon Animation
The Second Law
“The force exerted on a body is equal to
the mass multiplied by the acceleration.”
F = ma
In other words, the greater the force the
more the object accelerates.
Falling Bodies
Unchecked, the force
of gravitation causes
objects to accelerate
toward the center of
the Earth.
Without air resistance,
they fall at the same
rate. With air
resistance, less
massive objects slow
down.
The Third Law
“For every action there
is an equal and
opposite reaction.”
You push me and I
push you back!
Jet Propulsion
Binary Star Animation
Newton’s Law of
Universal
Gravitation
F=G•M•m
2
r
This means that objects with
high mass are strongly
attracted to each other.
The Tides
The farther apart the two
objects are, the weaker the
force of gravity.
SUN
MERCURY
NEPTUNE
This explains why planets
closer to the Sun move faster
than those farther away.
It also helps to explain Kepler’s
Third Law:
D3 = P2