Gravitational fields Flashcards
What is gravitational field
Object feels a non-contact force
Experience an attractive force
Describe the difference in field lines in a radial and uniform field
Radial- Towards the centre . As distance increases , field strength decreases
Uniform - Field lines are parallel and equally spaced apart . Field strength is constant at any point.
What is Newtons law of gravitation
What is field strength
What is the NLoG equation in a radial field.
What does this represent in a graph
g = GM / r^2
Inverse square law.
represent in a g against r graph
What is gravitational potential
Potential energy per unit mass.
V = -GM / r
Negative on the surface
WHy is gravitational potential negativee?
Negative at the surface and inc with distance from the mass.
Negative energy as having to do work against the gravitational field so Gravitational potential at infinity is 0.
It gains potential energy as it goes upwards so become more postive
Describe the Relationship in a V against r graph
G against r
g = -v / r
V/ r = Gradient at a point shows the value of g
g/r = Area under the curve shows gravitational potential
What is escape velocity>
How doe you derive escape velocity
Velocity where the kinetic energy is = gravitational potential energy. so total energy is 0
1/2mv^2 = Gmm/r
1/2v^2 = Gm/r
v^2 = 2GM / r
What is gravitational potential difference
Energy needed to move a unit mass from Infinity to a point in a gravitational field .
The centripetal force = gravitational force
Derive the relationship T^2 ~ r^3
mv^2 / r = Gmm / r^2
v^2 = Gmmr / r^2m
v = root / Gm / r
so v ~ to 1/root r
v =2πr / T
T^2 = 4π^2r^3 / GM
so T^2 ~ r^3
Describe Features of a geostationary satellites
Time period is 24 Hours
Always at the same point above the earth , directly above the equator. - DOn’t need to move aerial
What is the use of satellites
Cheaper to launch with low orbit satellites.
Useful for communications
Imaging satellites - Weather
