# Physics - Recall for Chapter 18; Gravitational Fields

## Flashcards

### 2022-04-23

What is a gravitational field?

A region in which a mass will experience a gravitational force.

What is gravitational field strength?

The force per unit mass exerted on a test mass at that point in the field.

What are the units of gravitational field strength?

What does the direction of a gravitational field line show?

The direction of force on a test mass at that point in the field.

What is represented by the spacing of field lines in a field line diagram?

Field strength.

What is a radial gravitational field?

A gravitational field produced by a point mass.

What does a radial gravitational field look like?

Many lines all pointing towards the centre of mass.

What is a uniform gravitational field?

A region in which the gravitational field strength is constant.

How is a uniform gravitational field shown in a field line diagram?

Parallel, equally spaced field lines.

What is a point mass?

An idealised mass with zero size.

What is Newton’s Law of Gravitation?

The gravitational attraction between two objects is proportional to the product of their masses and inversely proportional to the square of their separation

What is Kepler’s 1st law?

A planet’s orbits is an ellipse with the Sun at one of the two foci.

What is Kepler’s 2nd law?

The line segment joining a planet to the sun sweeps out equal areas in equal times.

What is Kepler’s 3rd law?

The square of orbital period is proportional to the cube of the average radius.

How does gravitational field strength vary with distance from a point mass?

It follows an inverse square law.

What are the three conditions for a satellite to be in a geostationary orbit?

- There’s a period of 24 hours
- It is above the equator
- It moves in the same direction as the Earth’s rotation

What is gravitational potential?

The work done per unit mass to move an object from infinity to a point in the field.

How does gravitational potential vary with distance from a point mass?

It is inversely proportional.

What is gravitational potential energy?

The work done to move an object from infinity to a point in the gravitational field.

What does the negative sign mean in the gravitational potential equation?

The force is attractive.

What does a plot of gravitational potential against distance show?

A negative hyperbola.