Gravitational fields

What is gravity?

Gravity is the universal attractive force which acts between all matter

What is G?

The universal gravitational constant

What can field lines tell you about a field?

The direction of the field and the strength of the field depending on the density of the field lines

What is g?

g is the force per unit area in a uniform gravitational field. In a radial field the magnitude of g is the proportionality constant at that point between force and mass. So g=GM/r²

What is newtons law of gravitation?

Newtons law of gravitation states that two point masses attract each other with a force that is directly proportional to the product of their masses, and inversely proportional to the square of the distance between them.

What is Keplers first law?

Keplers first law states that the orbit of a planet is an ellipse, with the sun at one focus. The eccentricity of the ellipse is very low, so the motion can be modelled as circular.

What is keplers second law?

Keplers second law states that a line segment joining a planet and the sun sweeps out equal areas during intervals of equal time. This is because the speed of the planet is not constant - the planet moves faster when closer to the sun

What is Keplers third law?

Kepler’s third law states that the square of the orbital period T is proportional to the cube of the average distance r from the sun.

What are satellites?

Satellites are objects that orbit other, larger objects. These can include natural satellites like the moon, and artificial satellites that humans have sent into space.

What are satellites used for?

Uses include: communications, scientific research and GPS

What are geostationary satellites?

Geostationary satellites have an orbital period that is exactly a day, so that they appear stationary above the earth.

What are the uses of geostationary satellites?

They are useful for communication and surveying as they provide continuous coverage

What is gravitational potential?

The potential energy per kilogram, at any point in the field. 0 potential is defined at infinity, so at a point close to a mass, the potential of an object would be negative.

What is gravitational potential difference?

Gravitational potential difference is the difference in the gravitational potentials of two points in a gravitational field.

What is gravitational potential energy at a point in a field?

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

What is escape velocity?

The minimum velocity an object requires in order to escape the gravitational field of an object when projected vertically from its surface.