Transcript 11.2 gravity

11-2
Newton
Gravity
Law of Universal Gravitation
• All objects in the universe attract each other
through gravitational force
• F= G m1m2
d2
F= force
G= constant of universal gravitation
(6.673 x 10-11 Nm2/kg2)
m-=mass
d=distance
All Matter is affected by gravity
• Gravity is easier to detect between large
objects than it is for small objects that is
why we notice the gravity on Earth but we
can not detect it for all objects.
Gravitation Force increases as
mass increases
Small mass=
small gravity
Large
mass=
large
gravity
Gravitational force decreases as
distance increases
Closer =
larger
force
Farther apart= smaller force
Free – Falling Acceleration
• As a body falls
though the air its
velocity
increases
(accelerates)
• (acceleration due
to gravity on
earth) g= 9.8
m/s2
All objects accelerate at the same rate
• If there is no air
resistance, all objects
fall at the same rate,
regardless of their mass
• An apple and a feather
dropped from the same
height will hit the
ground at the same
time if there is no air
resistance
Misconception!!
- Mass and Weight are the same thing.
Truth!!
- Mass is the amount of matter in an
object.
- Weight is the force of gravity on
an object.
Weight (or any force) is measured in
Newtons (N)
weight = mass x gravity
w = mg
g = 9.81 m/s2
• Mass does not
change with an
objects location
• Weight decreases
as you increase the
distance from the
center of the Earth.
Mass vs. Weight
• An anvil in outer • The astronaut in
space
finds
it
is
space may be
just as difficult to
weightless but it
shake the
is not massless.
“weightless” anvil
as it would be on
earth.
If the anvil is more massive than
the astronaut, which shakes
more, the anvil or the
astronaut?
• The difficulty of lifting an object
against gravity (weight) is
different than moving its mass