Ocean Tides

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Every object on the surface of the Earth feels
the force and this force is directed toward the
center of the Earth.
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What about accepting this idea force, acting at
a distance ?
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What is the Centripetal Acceleration of the Moon?
aM g/3600
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The Universal Law of Gravity
Force mass1 x mass2/distance2
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Newtons Law of Universal Gravitation
Every particle in universe attracts every other
particle with a force that is proportional to the
product of their masses and inversely
proportional to the square of the distance
between them. This force acts along the line
joining the two particles. F G m1m2/r2
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The Universal Gravitational Constant G
F Gm1m2/d2 G 6.67 10-11 Nm2/kg
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Gravity and DistanceThe Inverse Square Law
The inverse square law holds for gravity and for
all phenomena wherein the effect from a localized
source spreads uniformly throughout the
surrounding space the electric field of an
electron, light from a match.
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Questions

• If there is an attractive force between all
  objects, why do we not feel gravitating toward
  massive buildings in out vicinity?
• Consider an apple at the top of the tree that is
  pulled by Earths gravity with a force of 1 N.
  If the tree were twice as tall, would the force
  of gravity be only ¼ as strong? Defend your
  answer.

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• If Earth were hollow but still had the same mass
  and radius, would your weight be different? Why?
• Skylab caused quite a commotion when it returned
  to Earth in July 1979. Why would it suddenly
  return to Earth after it had been in orbit for
  many years?
• Why we use different formulas for gravitational
  force for object on the surface of Earth and for
  object far from Earth?

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Weight and Weightlessness
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To be more general we now refine the definition
of weight weight of something is the force it
exerts against a support.
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Question
In what sense is drifting in space far away from
all celestial bodies like stepping off the table?
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Question
We known that both the Moon and the Sun produce
our ocean tides, and we know that the Moon plays
the greater role because it is closer. Does it
closeness mean it pulls with more gravitational
force than the Sun on the Earth oceans?
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Ocean Tides
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Tides in the Earth and Atmosphere
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Tides on the Moon
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Gravitational Fields
The field concept plays in-between role in our
thinking about the forces between different
forces.
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Gravitational Field Inside of Planet
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Your acceleration will be progressively less as
you continue toward the center of the Earth.
Why???
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Black Holes
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How may a black hole detected if there is
literally no way to see it?
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Universal Gravitation
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Why is our Earth round?