Transcript Newton`s Law of Gravitation

Monday, February 17th
Copy equations from notes onto your
own paper. Also, copy any other
information you think you might need as
you go through this power point with
sub. After the power point, you will be
given an assignment.
Newton’s Law of Gravitation
G= 6.67 E -11 Nm2/kg2
AKA Gravitational Constant
This equation can be used to find the force of
attraction between any two objects. R should
be the distance between the objects from
center to center. Both objects will have the
same magnitude of force on each (Newton’s 3rd
law)
2
Fg=mg=GMm/R
We can equate mg with Newton’s Law of
Gravitation equation when an object is near
the surface. M= mass of planet, R= radius of
planet, m=mass of object (which cancels)
If object is not near surface, radius of planet
would need to be added to height above
planet.
2
F=GMm/R =
2
mv /R
We can equate Newton’s Law of Universal
Gravitation with the centripetal force
equation when working with objects in orbit
(like satellites or planets)
M= mass of larger object such as earth
(compared to satellite traveling around
earth), m= mass of satellite, R is distance
from center to center. Notice mass of object
that is orbiting is cancelled out. Mass of
object that is being orbited is important.
Kepler’s First Law: The path of the
planets about the sun is elliptical in
shape, with the center of the sun
being located at one focus.
Kepler’s Second Law: An imaginary line drawn from
the center of the sun to the center of the planet will
sweep out equal areas in equal intervals of time. In
other words, the planet moves faster as it gets closer
to the sun and slower as it gets farther from the sun.
More KE closer to
sun and more PE
further from sun.
The ratio of the squares of the periods of
any two planets is equal to the ratio of the
cubes of their average distances from the
sun
I don’t think you will be using this equation
for AP, but if you do, the first thing you
should do is take off the parenthesis above
and square everything separately- like the
picture to the right.
Assignment:
Each student needs to get a buff colored (NOT
YELLOW) GRAVITATION packet from the front of the
classroom in the bins near the door. Get both the
question and the answer packet (both buff in color).
Spend the rest of class working on both MC and FR
parts of the packets. Quiz next class over torque and
gravitation.