The Gravitational Feild Flashcards
Chapter 5
Gravitational Feild
The region or space around which a mass experiences force due to the gravitational attraction of another mass
Newton’s Law of Gravitational Attraction
This states that the gravitational force of attraction between two-point masses is proportional to the product of the mass and inversely proportional to the square of their separation distance
Newton’s Law of Gravitational Attraction: Mathematically
a
F ∝ m1, m2
F ∝ 1/r²
F = (m1 m2) / r²
[K = G]
G > universal gravitational constant
G= 6.67x10⁻¹¹ Nm²/Kg²
What happens to the force due to gravity when the masses are twice as far away?
It reduces
Gravitational Feild Strength
Gs = Fg/m (N/ kg)
Fg = force due to gravity or weight
Kepler’s Law: First part
Planets revolves in an elliptical orbit
Kepler’s Law: Second Part
Each planet revolves in such a way that the imaginary line joining it to the sun sweeps out equal areas unequal times
Kepler’s Law: Third Part
The square of the periods of revolution of the planets are proportional to the cubes of their mean distances from the sun.
T² ∝ r³
Know the proof of Kepler’s Third Law
a
Proof = Fg = Fc
(G me ms)/ r² = (ms v²) / r
Once they are set equal, ms and Ms cancel each other. r cancels one r
(G me) / r = v²
Since v = 2πr/T
(2πr/T)² = (Gme/r)
4 π² r² / T² = Gme / r
Cross multiply with the intention of isolating T²
4 π² r² (r) = Gme (T²)
4 π² r³ = Gme (T³)
Divide both side by Gme
T³ = (4 π² r³) / Gme
Since k = (4 π²) / Gme
T² = Kr³
T² ∝ r³
Define artificial satellites
It is a huge body that moves around a planet in an orbit due to the force of gravitational attraction
Define parking orbit
A parking orbit is a path in space of the satellite which makes it appear to be in the same position, relative to the observer at a point.
Uses of parking orbit
1) many geostationary satellites are required for efficient broadcasting
2) communication can only occur provided, there is no obstruction between the transmitter and the receiver
Examples of Parking Orbit
