Gravitational Fields Flashcards
State Newton’s Law of Gravitation
Every particle attracts every other particle with a force that is proportional to the product of their masses and inversely proportional to their separation squared.
What is a gravitational field?
A region where an object with mass will experience an attractive non-contact force due to gravity.
What does the negative sign show on the formula?
That it is an attractive force because F is in the opposite direction to r.
What can we assume about gravitational field at Earth’s surface.
Perfectly uniform, field lines parallel and equally spaced
What is gravitational potential?
The work done in moving a unit mass from infinity to that point.
How do you derive escape velocity formula?
mv^2/2=Gmm/r
What is a satellite?
A smaller mass that orbits a larger mass.
What is the speed of a planet’s orbit defined by?
centripetal force = attractive force, so v=√GM/r
What is a geostationary satellite?
Orbits directly over the equator above the same point on Earth - 24 hours
Kepler’s First Law?
Each planet moves in an ellipse around the Sun, with Sun at one focus.
Kepler’s Second Law?
A line joining the Sun to a planet will sweep out equal areas at equal time intervals.
Kepler’s Third Law?
The period of the orbit squared is proportional to the mean distance between sun and planet cubed.
What is gravitational field strength?
The force of attraction per unit mass.
What is a Lagrange point?
Points where object is pulled by gravity but there is no resultant force.
When an astronaut is in the International Space Station, the gravitational force acting
on him is 90% of the force acting on him when he is on the Earth’s surface.
Why does the astronaut imagine himself to be weightless?
The astronaut has centripetal acceleration = space station so only feels forces applied by contact with the walls of the space station, no support force from the space station
