Gravitational Fields Flashcards
Formula for gravitational field strength at a point in a gravitational field
g=F/m
What are gravitational field lines like on the surface of the earth
Uniform
What do all gravitational field lines point towards
The centre of mass of the the object creating the gravitational field
Equation for Newton’s law of gravitation
F=-GMm/r^2
What is the value and units of G
6.67 x 10^-11
Nm^2kg^-2
What does the negative sign show in Newton’s law of gravitation
That it is an attractive force
What is the formula to find gravitational field strength in a radial field
g=-GM/r^2
Kepler’s first law
The orbit of a planet is elliptical with the sun at one of two foci
Kepler’s second law
Line segment joining the planet and sun will sweep out equal areas during equal intervals of time
Keplers third law
T^2 is directly proportional to r^3
What is the astronomical unit
The mean distance between the earth and the sun
Equation to find the speed of an object in orbit
v^2 = GM/r
Equation for the pro oral time period of an object in orbit
T^2 =4pi^2r^3/ GM
Do keplers laws apply to smaller objects in orbit eg satellites and moons?
Yes
Sea of satellites
Communication, weather, pictures, research
3 conditions for a geostationary orbit
- be in orbit above the equator
- orbital period of 24 hours
- rotate same direction as earth
Symbol of gravitational potential
Vg
What is Vg defined as?
The work done per unit mass to move an object to that point from infinity
Is gravitational potential scalar or vector
Scalar
Equation for gravitational potential
Vg= -GM/r
Why is Vg always negative
Work is done to move one object away from another. Vg at infinity is a maximum of 0, so all values is negative as work is done to move it away from that point
Equation for gravitational potential energy in a uniform gravitational field
Ep=mgh
Equation for gravitational potential energy in a radial field
E=mVg
Equation for escape velocity
v^2=2GM/r
