Essay About External Force And Gm1 M2

The Wonders Of Astronomy
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Some Formulas: a) Powers of Ten: 1 = 100 ; 1,000 = 103 ; one million = 1,000,000 = 106
b) Geometry: Circles: Area = pr2
Perimeter = 2pr
Spheres:
Volume = 4/3pr3
Surface Area = 4pr2
c) Laws of Motion:
Time = Distance/Speed or Distance = Rate x Time
1 Year = 3.16 x 107 sec
1 AU = 1.5 x 108 km
1pc = 3.26 ly = 206265 AU
d) Keplers and Newtons Laws: P2(yr) = a3(AU)
F = ma
FG = Gm1 m2 / r2 e) Light, Waves:
Speed of light c = 3 x 105 km/sec = 300,000 km/sec = 186,000 miles/sec f) Telescopes:
Light Gathering Power -> Area g) Magnification = (Focal length of the Objective) /
(Focal length of the Eyepiece) General Knowledge: COVER ALL THE TOPICS IN THE SYLLABUS! *
Who were Aristotle, Eratosthenes, Ptolemy, Galileo, Kepler and Newton and what were
their main contributions to science?
Aristotle (350 BC)
Greek Philosopher
Believed the Earth is at the center of all orbits
Geocentric System
Eratosthenes (200 BC)
Greek astronomer and mathematician
First to measure the Earth?s diameter
Ptolemy (140 AD)
Retrograde Motion – Planet appears to be moving backwards from the view of the Earth.
Theory of Epicycles – a small circle, riding on a larger circle called the deferent, on
which a planet moves. The epicycle is used to account for retrograde motion.
Heliocentric System
Galileo
Credit for first using a telescope to make astronomical studies
Observed the moon
Observed that the apparent size of Venus changes for different phases
Studied projectiles
Dropped two balls from one point and discovered they fell at the same speed. Arrested
and tried for stating that the Earth moved.
On his death bed said, ?Epur Si Muave? = It?s still moving.
Kepler ?Kepler?s Supernova?
Kepler?s Laws of Planetary Motion
The orbit of the planets are ellipses – NOT CIRCLES with the Sun located at one of the
focus of the ellipse. A line from the planet to the sun sweeps over equal areas in equal
intervals of time. Hence, the planet moves faster when closer to the Sun.
A planets orbital period squared is proportional to its average distance from the Sun
cubed: P2 (years) = a3 (AU)
Newton
The Giant of the 18th Century
Most influential scientist to ever live
Explained Kepler?s Laws
Newton?s Laws of Motion
A body continues at rest or in uniform motion in a straight line unless acted upon by
some external force
A bodies change of motion is proportional to the force acting on it and is in the
direction of the force
When a body exerts a force on a second body, the second body must exert an equal and
opposite force back on the first body
Newton?s Law of Gravitation
The force is proportional to the PRODUCT of the masses. That is, the force with which,
say the Sun acts on a Planet, is proportional to the mass M1 of the Planet and to the
mass M2 of the Sun. The force is inversely proportional to the SQUARE of the Sun-Planet
distance r. If the distance between the Sun and the Planet is increased by a factor of
two, the force becomes 4 times smaller (weaker). The force is always ATTRACTIVE: the Sun
wants to “engulf” the Planet – it never pushes it away. G is a UNIVERSAL constant:
G=6.672×10-11 m3/kg/s2 It is the same for any two objects in the Universe!!!
Invented Calculus
* Constellation, the celestial equator, the ecliptic, the celestial poles, right
ascension and declination.
Constellation – One of the 88 areas into which the sky has been divided for convenience
in referring to the stars or other objects therein.
Celestial Equator – The intersection of the celestial sphere with the plane that passes
through the Earth?s equator.
Ecliptic – The path followed by the Sun across the celestial sphere in the course of a