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Lecture12 (Topic11) Gravitation, NG HUI YUN A20SC0187 - Coggle Diagram
Lecture12 (Topic11)
Gravitation
Newton's Law of Universal Gravitation
G = 6.67×10^(-11) Nm²/kg²
vector form
Satellites
Satellite is put into orbit by accelerating it to a sufficiently high tangential speed with use of rockets.
speed too high, escape from the Earth
speed too low, return to the Earth
In fact, satellite is falling (accelerating towards the Earth) but high tangential speed keeps it from hitting the Earth
'Weightlessness'
free fall in elevator
people in satellite close to the Earth
(satellite acceleration = acceleration of gravity)
(objects/people within satellite - same acceleration)
Kepler's Law
1st law: path of each planet about the Sun is an ellipse with the Sun at one focus
2nd law: each planet moves so that an imaginary line drawn from the Sun to planet sweeps out equal areas in equal periods of time
3rd law: ratio of squares of periods of any 2 planets revolving about the Sun = ratio of cubes of their semimajor axes
Gravitational Field
surrounds every object that has mass
gravitational force per unit mass at any point in space
Types of Forces in Nature
gravitational force
electromagnetic force
strong nuclear force
weak nuclear force
Principle of Equivalence;
Space Curvature;
Black Holes
Principle of Equivalence
equivalence between inertial and gravitational mass
Space Curvature
curvature is greatest near very massive objects
Black Holes
a star that becomes so dense and massive
very strong gravity (even light couldn't escape)
if objects too close to it, they would be swallowed up and never to escape
NG HUI YUN
A20SC0187
