Field Theory Answers

Assuming that the planets are moving in circular orbits, apply Kepler's laws to show that the acceleration of a planet is inversely proportional to the square of its distance from the sun.

Briefly describe an experiment by which the value of g may be determined. Indicate the measurements taken and how to calculate the result.

Distinguish between the gravitational constant (G) and the acceleration due to gravity (g) and show the relation between them.

How can you account for the sensation of 'weightlessness' experienced by the occupant of a space capsule
(a) in a circular orbit round the earth
(b) in outer space? Give one other instance in which an object would be 'weightless'.

Assuming that the mean density of the earth is 5500kgm^-3, that the constant gravitation is 6.7 x 10^-11 Nm^2kg^-2, and that the radius of the earth is 6400km, find a value for the acceleration due to gravity at the earth's surface.

If the acceleration due to gravity is 98m/s^2 and the radius of the earth is 6400km, calculate a value for the mass of the earth.

Calculate the force of attraction between two small objects of mass 5kg and 8kg respectively which are 10cm apart. (G = 6.7 x 10^(-11) Nm^2kg^-2. Comment on the value of your answer.

A satellite of mass 200kg is placed into Earth orbit at a height of 200km above the surface.
(a) Assuming a circular orbit, how long does the satellite take to complete one orbit?
(b) What's the satellite's speed?

A 1000kg satellite orbits the Earth at a constant altitude of 100km.
(a) How much energy must be added to the system to move the satellite into a circular orbit with altitude 200km?

How much energy is reqyired to move a 1000kg object from the Earth's surface to an altitude twice the Earth's radius?