Fast Moving Projectiles: Satellites

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Fast Moving Projectiles Satellites
The Earth satellite is simply a projectile that
falls around the Earth rather than into it.
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A common misconception is that satellites
orbiting at high altitudes are free from
gravity. The high altitude only allows the
satellites to go above atmosphere, but they are
in the field of the Earth gravity.
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Question
A newspaper report reads in part, The space
shuttle orbits Earth at an altitude of nearly 200
miles and is traveling at a speed of 18,000 mph.
The shuttle remains in orbit because the
gravitational force pulling it toward Earth is
balanced by the centrifugal force (the force of
inertia) that is pulling it away from Earth.
Explain why this newspaper should hire a new
reporter.
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Questions
A vine is just strong to support Tarzan when he
is hanging straight down. However, when he tries
to swing from tree to tree, the same vine breaks
at the bottom of the swing. How could it happen?
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A common misconception is that satellites
orbiting at high altitudes are free from
gravity. The high altitude only allows the
satellites to go above atmosphere, but they are
in the field of the Earth gravity.
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Rotational Motion
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Aristotle There are two sets of natural laws
one for earthly events, and another, altogether
different, for motion in the heavens.
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The Concept of Gravity
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Newtons Law of Universal Gravitation
Whenever a body has a force exerted on it, that
force is exerted by some other body.
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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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Question

1. The Moon falls around the Earth than straight
   into it. If tangential velocity were zero, how
   would the Moon move?
2. According to the equation for gravitational
   force, what happens to the force between two
   bodies if the mass of one of bodies is doubled?
   If both masses are doubled?

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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

1. If there is an attractive force between all
   objects, why do we not feel gravitating toward
   massive buildings in out vicinity?
2. 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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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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Ocean Tides
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Question
We know 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?