Chapter 4 - Gravitational Fields Flashcards
(11 cards)
State one difference between an electric field and a gravitational field
An electric field can be attractive and repulsive, whereas gravitational fields are only ever attractive
State Newton’s law of gravitation
Two masses attract each other by a force which is proportional to the product of their masses and is also proportional to the inverse square of the distance between their centre of masses
Explain the significance of the -ve sign in the equation for gravitational field strength (g)
It shows that the potential gradient is in a positive direction upwards, and the gravitational field direction is downwards
What is potential gradient?
The change of potential per metre at a point in a gravitational field
Equation for escape velocity
V = (2GM/r)^1/2 V = (Root) 2GM/r
In which direction do gravitational field lines go?
Towards the centre of mass
Define escape velocity
The minimum velocity an object must have at the surface of a planet to escape the pull of gravity using its own kinetic energy
Define gravitational potential, V, at a point
The work done per unit mass to move an object from infinity to that point
What is the value of gravitational potential at infinity?
0 (Zero)
What is Kepler’s 3rd. law?
The time period squared of an orbit is proportional to the radius cubed of the orbit
How much work is done when moving along an equipotential line?
0 (Zero)
