{Year 2} Chapter 3 - Gravitation (Halfway down pg47) Flashcards
Why does the moon have a smaller surface gravity than the Earth?
As it is a less massive body
What is Newton’s Law of Gravitation?
F = (m1)(m2)G / r^2
What is G?
The universal constant of gravitation - 6.67 x 10^-11
When can Newton’s Law not be applied, and why?
When the two masses are irregularly shaped unless a complicated summation of the forces is made - since the law only works for point masses, or spheres since they act as if their mass was concentrated in the middle
What law does gravity, like light, obey?
The inverse square law
What is a gravitational field?
A region in space in which a massive object experiences a gravitational force
What is field strength?
The strength of the gravitational field measured in N/kg. Field lines represent the direction and strength of the field
What is the equation for gravitational field strength?
g = F/m
What happens to the gravitational field near the surface of a planet?
It becomes very nearly uniform - meaning that the field is of the same strength and direction everywhere
What is the difference in the way gravitational field lines are drawn when the field is half as powerful?
The lines are half as prevalent/half as many of them
When is capital M used in equations in gravitation?
For the mass of a large object such as a star or a planet
What is the equation for the volume of a sphere?
V = 4/3 x Pi x r^3
What is the equation for gravitational potential energy?
Grav. pot. = mass x gravity x difference in height
What is gravitational potential difference?
The gravitational potential energy difference per kilogram. Gravitational potential and potential difference have units of J/kg. It’s symbol is Delta V
What is an equipotential surface?
A surface along which if you move, the gravitational potential stays the same
What is the equation which links gravitational fields and potential?
g = - Delta V / Delta h
What is escape velocity?
The minimum velocity an object must have at the surface of a planet to escape the pull of gravity using its own kinetic energy
What is the set of equated equations or single one that one can use to calculate the escape velocity for a planet?
1/2mv^2 = m DeltaV = GMm/r OR v^2 = 2GM/r
What is the equation linking velocity^2 and G?
v^2 = GM/r
Which is faster - a larger or smaller orbit?
The smaller orbits are faster
What is the equation linking time period and 4Pi^2?
T^2 = (4Pi^2/GM)r^3
Why can’t GPE = mgh be used for satellites or large objects?
As the large distance changes in height they would go through would result in a fluctuation in the strength of the gravitational field strength - g would not be constant
What is the point in an object’s orbit that is closest to the Sun called?
The perihelion, and the furthest away the aphelion
When an object such as a comet moves in an elliptical orbit, what happens to its energy?
It stays the same, although its speed changes
