Gravitational Fields Flashcards
What does Newton’s Law of Gravitation state?
- that force (between two masses) is:
- directly proportional to the product of the masses
- inversely proportional to the separation of the centres squared
- always attractive
Define a force field
a region in which a body experiences a non-contact force
What type of quantity is a force field?
a vector quantity
What does the gradient of a force-mass graph tell us?
the gravitational field strength
Define a gravitational force field
a region in which an object with mass experiences weight
Define gravitational field strength
the force per kg acting on a small test mass at a point in a gravitational field
Define gravitational potential
the work done per kg in bringing a small test mass from infinity to that point in the gravitational field
Why are GPE and gravitational potential always negatve?
- because gravity causes an attractive force
For a radial field, what happens to the equipotential lines as r (radius) increases?
the spacing between equipotential lines increases
What does the gradient of a V against r graph represent?
gravitational field strength (can be seen by formula sheet)
Define escape velocity
the minimum speed an unpowered object needs in order the leave the gravitational field of a planet (or star)
Where does a polar orbit go?
passes over both poles
Are polar orbits high Earth orbits or low Earth orbits?
LEO (Low Earth Orbits)
What is the 2 main advantages of a polar orbit?
- with a polar orbit, a satellite can cover the whole Earth as the Earth rotates
- also have short time periods, around 1.5 hours
Give 3 uses of polar orbits
- mapping
- weather
- reconnaissance (spying)
