Gravitational Fields Flashcards
Newtons law of gravitation.
Any two point masses attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of their separation.
What is gravitational field strength?
The g.f.s at a point is the gravitational force exerted per unit mass on a small object placed at that point.
Value of gravitational constant.
6.67 x 10¹¹(negative)Nm²/kg²
Twice as far away gives?
One quarter of the force.
Equation of gravitational force between masses.
F = Gm₁m₂/r²
Equation of gravitational field strength (g).
g = GM/r²
Why isn’t g a constant?
Because it decreases as distance r increases
Why isn’t it suitable to use “g.p.e=mgh” for calculating gravitational energy.
- It is fine when considering objects near the earths surface, but is insignificant if we are considering objects through space.
- If we lift an object to a great height, g decreases, we would need to take this into account while calcing g.p.e
What is gravitational potential?
The gravitational potential at a point is the work done per unit mass in bringing a mass from infinity to that point.
What happens when a mass is brought towards another mass.
It’s g.p.e decreases.
What is a geostationary orbit?
A special kind of orbit in which a satellite is positioned so that, as it orbits, the earth rotates below it at the same rate. It remains at a fixed point above the equator.
Equation used for geostationary orbits.
T² = (4π²/GM) r³
Equation to find speed of a satellite .
v² = GM/r
