Transcript Gravity - PhysicsAPB

Gravity
Find the gravitational
attraction of the moon to the
Earth using the regents
reference tables.
What would the gravitational
attraction of the Earth to the
moon be?
What if the moon where
twice as massive?
Gravity
What if the moon where
twice as massive?
Find the gravitational
attraction of the moon to the
F = G x M 1 x M 2 / r2
Earth using the regents
= (6.67 E-11) x (7.35 E22) x (6.37 E24)
reference tables.
(3.84 E8)2
What would the gravitational
attraction of the Earth to the
moon be?
= 2 billion billion Newtons
What happens to a person’s weight at an
altitude of 1 earth radii?
Find the attraction of a 50 kg satellite at 1 earth radius above the earth.
Find the gravitational attraction between
these two masses?
Find the gravitational attraction
between an electron and a proton in
a hydrogen atom ( r = 10-6 m ).
Henry Cavendish’s experiment to measure G .
How is gravity involved in creating the tides?
M
Find the total gravitational force on the 30
kg sphere due to the other 2 spheres.
To achieve orbit, you must launch a rocket at a certain
minimum velocity, called the orbital velocity, where the
object’s weight can provide the centripetal force, and the
earths curvature makes up for the objects falling.
Fc = W
mv2 = mg
r
vescape = gr
The “force field” model:
A drawing wher arrows represent the direction oif the force on an
object. The denser the lines, the stronger the field and the stronger the
force
g=
Fg
m
g = 2.5
g=6
g = 9.8
g = 9.81 N/kg
G is relatively constant at 9.81 N/kg
near the surface of the earth.
Sensitive gravimetric measurements show variation of g at
different points on earth’s surface at the 5th decimal place
Gravitational Map of New England
Why is the gravity stronger over oceans?
VERY exaggerated graphics of where g is strongest and weakest on
earth’s surface, due mainly to variances in local rock densities.
A 50 kg mass experiences a weight of 1,000 Newtons on planet X.
Find the gravitational field strength on planet X.
What is the acceleration of gravity on planet X?
Kepler’s Laws of
Motion
LAW 1: The orbit of a planet is an ellipse with the Sun's center of mass
at one focus
LAW 2: Planets sweep out equal areas in equal intervals of time
LAW 3: The squares of the periods of the planets are proportional to the
cubes of their distance to sun:
Ta2 / Tb2 = Ra3 / Rb3
Ta2 / Tb2 = Ra3 / Rb3
Planet
Period
“T”
a
(AU)
(yr)
Neptune is 30 times further
from the sun than we are.
Calculate its period of orbit.
Neptune is 30 times further
from the sun than we are.
Calculate its period of orbit.
Mercury 0.24
0.39
Venus
0.62
0.72
Earth
1.00
1.00
Mars
1.88
1.52
Jupiter 11.9
5.20
Saturn 29.5
9.54
T2
R3
Neptune is 30 times further than we are from the sun.
Calculate its period of orbit.
In another solar system, planet X is 5 times farther away from its
central star than planet Y. Planet X has a solar year of 500 days. Find
the period of planet Y.