Gravitational Fields

Question 1

Gravitational Potential

Answer 1

Work done in moving a unit mass from infinity to that point in the gravitational field (scalar)

Question 2

Gravitational Potential Energy

Answer 2

Energy stored in an object (work an object can do) by virtue of the object being in a gravitational field (scalar)

Question 3

Gravitational Field Strength

Answer 3

Force per unit mass (at a point in a gravitational field).

Question 4

Kepler’s First Law

Answer 4

The orbit of a planet is an ellipse with the sun at one of the two foci

Question 5

Kepler’s Second Law

Answer 5

A line segment connecting a planet to the sun sweeps out equal areas in equal time periods

Question 6

Kepler’s Third Law

Answer 6

T^2 d.p. R^3

Question 7

Geostationary Satellite

Answer 7

Remains in same position relative to spot on earth’s surface, over equator, time period synchronous to earth’s rotation.

Question 8

Escape Velocity

Answer 8

Minimum velocity at which an object has just enough energy to leave a specified gravitational field.

Question 9

Why are all Gravitational Potentials negative?

Answer 9

GPE at infinity is zero.
Work must be done against attractive forces to move a mass from a point in space to infinity, so the GPE at the initial point must be less than zero; negative.