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Gravity
• Any two objects are attracted
to each other simply because
they have mass.
Universal Law of Gravitation
• Gravitational force is a field force between two particles -- in all
mediums.
• Force varies as the inverse square of the distance
• Force is proportional to mass of objects
=
∙
= 6.67 × 10 • G is the Universal Gravitational Constant.
• Gravity force acts from the center of object.
EE Button?
Laws of Attraction
• Girl, Brandy (42.5 kg), sits 1.50 m from boy
(63.0 kg), George. What is force of gravity
between them?
Laws of Attraction
• Girl, Brandy (42.5 kg), sits 1.50 m from boy
(63.0 kg), George. What is force of gravity
between them?
Find mass of earth. re = 6.38 x 106 m. 10.0 kg
mass, other mass is earth’s mass.
Find mass of earth. re = 6.38 x 106 m. 10.0 kg
mass, other mass is earth’s mass.
You weigh 567 N on earth. How much would
you weigh on mars?
= . × = . ! × You weigh 567 N on earth. How much would
you weigh on mars?
= . × = . ! × What is the acceleration of gravity on Venus?
"#$% = . && × "#$% = . ' × What is the acceleration of gravity on Venus?
"#$% = . && × "#$% = . ' × The International Space Station has a
mass of 450,000 kg and 250 miles
(402,336m) above the surface of the
earth re=6.38x106m.
What is the force of gravity on it if the mass of the Earth is 5.97 x 1024 kg?
How fast is the ISS traveling?
How long does it take to orbit the Earth once?
The International Space Station has a
mass of 450,000 kg and 250 miles
(402,336m) above the surface of the
earth re=6.38x106m.
What is the force of gravity on it if the mass of the Earth is 5.97 x 1024 kg?
( = .
450,000
∗
5.97
∗
10
( = 6.67 ∗ 10
= 3.9 ∗ 102 2
402,336 + 6.35 ∗ 10
How fast is the ISS traveling?
( = 3
450000 ∗ 4 3.9 ∗ 10 =
(402,336 + 6.35 ∗ 102 )
2
4 3.9 ∗ 10 =
2
4 = 7664
7
How long does it take to orbit the Earth once?
897:;<=> = = = 2?
2? 402,336 + 6.38 ∗ 102 = 4.26 ∗ 10A
8 4.26 ∗ 10A
:= =
= 55607 = 92.79<
4
7664
402,336m
6.35E6m
Satellites
• http://waowen.screaming.net/revision/force&
motion/ncananim.htm
Gravity in orbit:
FreeFall
Astronauts ≡ "weightless"
distance to the center of the earth is only about 10 % greater
force of gravity only slightly less
Falling endlessly around the earth
Gravity doesn't seem to work while falling.
weightlessness is caused by being in a constant state of free fall.