Gravitational field

Question 1

What is a gravitational field

Answer 1

An area around a mass of which a gravitational force acts

Question 2

What do gravitational field lines show

Answer 2

The direction of the force on a small test mass

Question 3

describe two essential features of a sattelite for it to be geostationary

Answer 3

• must stay above the same point above the equator

- it’s orbit needs to be the same time period as one rotation of the earth

Question 4

what is a radial field?

Answer 4

a field in which the field lines are straight and converge or diverge as if from a single point

Question 5

what is a uniform field?

Answer 5

a region where the field strength is the same in magnitude and direction at every point in the field

Question 6

what is gravitational potential?

Answer 6

the work done per unit mass

when moved from infinity to a point

Question 7

what is newtons law of gravitation

Answer 7

• the force of attraction between two point masses
• proportional to product of masses
• inversely proportional to square of distances between them

Question 8

describe two advantages of geostastionary orbit

Answer 8

• offers uninterupted communication between transmitter and reciever
• steerable dish is not nessacery

Question 9

describe and explain what happens to speed of a sattelites orbit when it get’s closer to the planet it is orbiting

Answer 9

• speed increases

- loses potential energy but gains kinetic energy

Question 10

why do rockets launched from the earth’s surface not have to achieve escape velocity

Answer 10

• energy is continually added in flight

- they are not escaping the gravitational field

Question 11

what is gravitiaional field strength

Answer 11

the force per unit mass on a small mass placed in a gravitional field

Question 12

what is a satellite

Answer 12

any smaller mass which just orbits a much larger mass

Question 13

what is escape velocity

Answer 13

the minimum velocity an object must be given to escape from the planet when projected vertically from the surface

Question 14

what is an equipotential

Answer 14

line or surface in a field alogn which the electric or gravitational potential is constant

Question 15

what is a low orbiting satellite

Answer 15

any satellite which orbit between 180 and 2000km above the earth

Question 16

what is a synchronous orbit

Answer 16

an orbit when an orbiting object has an orbital period equal to the rotational period of the object it’s rotating

Question 17

in an eliptical orbit how does the kinetic and potential energy of a satellite change

Answer 17

it will speed up as it’s orbital radius decreases so kinetic energy increases as potential energy decreases.Total energy remains constant

Question 18

what is the key difference between electric and gravitational fields

Answer 18

gravitational forces are always attractice

electrostatic forces can be attractive or repulsive.

Question 19

why is gravitational potential negative

Answer 19

as work is done against the gravitational field to move the object out of it