Gravitational Fields Flashcards
Define gravitational field strength.
Force per unit mass.
Describe how a mass creates a gravitational field in the space around it
All matter produces a gravitational field, and the strength of it depends on how massive the object is.
How do we use gravitation field lines to represent gravitational fields?
The lines, and the arrows on them represent the direction of the gravitational field. The closeness of the lines represent the density. Gravitational field lines must always be drawn perpendicular to the object the refer to.
State Newton’s law of gravitation.
Any two point masses exert a force that is proportional to the product of their masses and inversely proportional to the square of their separation.
What is gravitational field strength like close to the earth?
Uniform, and approximately equal to the acceleration of free fall.
How can we see that objects orbit in nearly circular paths?
The gravitational force of the larger body is acting perpendicularly towards it at all times. Objects in orbit always have the same linear velocity, but their directions are constantly changing. So, we can equate gravitation force to centripetal force, meaning it’s path is almost circular.
Define the period of an object describing a circle.
The time taken for one complete orbit.
How we can we derive T^(2)=(4pi^(2)/GM)r^(3)?
Equate gravitational force to centripetal force, and rearrange for velocity. Then, sub this expression into the equation for the period of a circular orbit, which can be derived from the equation speed=distance/time.
What is a geostationary satellite?
A satellite with the same angular speed as the Earth. It orbits directly above the equator and is always at the same point above the Earth.
State Keplar’s third law.
The square of the period of orbit is directly proportional to the cube of the mean distance between the objects.
Give a use of a geostationary satellite.
TV and telephone signals. You don’t have to alter the angle of the receiver to keep up with the satellite.
