Gravitational Fields Flashcards
Explain what is meant by the statement:
The gravitational potential at the Earth’s surface is -62.7 x 106 J kg-1.
Grav. potential Vg at a point is defined as the work done to bring 1 kg from infinity to that point in space;
(G) force is attractive so the work done is negative (as separation is decreasing);
Vg is given the value zero at infinity so is negative nearer the Earth
Explain how Newton’s law of gravitation is applied between two non-spherical asteroids.
Force is proportional to the product of the mass of each asteroid and is inversely proportional to the distance squared between the centers of mass of the asteroids
(GMm)/r^2
Describe the similarities and the differences between the gravitational field of a point mass and the electric field of a point charge.
Similarity: The field strength or force is proportional to 1/separation^2 or both produce a radial field.
Differences: 1. Gravitational field is linked to mass the electric field is linked to charge. 2. Gravitational filed is always attractive whereas the electric field can be either attractive or repulsive.
Define gravitational field strength g.
The gravitational force experienced per unit mass on a small object at that point
What are Kepler’s three laws?
- All planets move in elliptical orbits, with the Sun at one focus.
- A line that connects a planet to the Sun sweeps out equal areas in equal times.
- The square of the orbital period of any planet is directly proportional to the cube of the mean distance from the Sun.
What is a geostationary orbit?
An orbital period of 1 day round the Earth. The satellite travels in the same direction as the rotation of the Earth and has its orbit in the equatorial plane of the Earth
What is gravitational potential?
The energy needed to bring a unit point mass from infinity to a given location.
What is Newton’s Law of Gravitation?
The force between two point masses, a distance d apart is given by F = (GMm)/(d^2)
