SP5b Gravity and Orbits

Question 1

The value of g on the surface of any body is always attractive and depends on what?

Answer 1

.the mass of the body
.the distance from its centre to its surface (the radius)

Question 2

The greater the mass and the smaller the radius of a body, the ? the value of g

Answer 2

greater

Question 3

Polar orbit uses?

Answer 3

.monitoring weather
.military applications (spying)
.imaging Earths surface

Question 4

Geosynchronous orbit uses?

Answer 4

.communications

Question 5

Geostationary orbit location and use?

Answer 5

.circular orbit fixed over one point on the earth
.for TV broadcasting

Question 6

Low earth orbit use?

Answer 6

.most satelites are in the LEO, including ISS

Question 7

Explain why the velocity of a planet changes even if orbiting at a steady speed?

Answer 7

A body moving at a constant speed in orbit, is accelerating because its direction is continually changing, so velocity is changing.
Acceleration requires a force, and for a planet it is towards the centre of a star (the centripetal force) – the gravitational force between the two bodies.

Question 8

Describe how changing the speed of an orbiting body affects the radius of its orbit.

Answer 8

If a satellite slows down the instantaneous velocity will not be large enough to hold it in its current orbit so it will fall towards Earth.
However, as it moves towards Earth, gravity will accelerate it down and when the effects of its speed end, the gravity force on it are once again balanced, it will settle into a new lower orbit.

Question 9

Explain how the radius of a stable orbit is affected by the orbital speed?

Answer 9

For an object in a stable orbit, if it is moving faster, the radius of its orbit must be smaller, because the gravitational force is greater, and vice versa.