gravitational fields

Question 1

what is gravity?

Answer 1

a force that acts between any 2 masses

Question 2

does the gravitational force attract or repel

Answer 2

attract

Question 3

when does the gravitational force increase

Answer 3

increases nearer the 2 bodies or when the bodies have large mass

Question 4

what happens to gravitational field as you move away from the object

Answer 4

strength of field reduces

Question 5

what direction does gravitational force act towards

Answer 5

always downward towards centre

Question 6

what is newtons law of gravitation

Answer 6

• force is directly proportional to the product of the masses
• force is inversely proportional to the square of the separation between 2 masses

Question 7

what does closer Field lines mean?

Answer 7

closer the field lines are together the denser the gravitational field

Question 8

what is escape velocity

Answer 8

escape velocity refers to the minimum velocity an object must reach to break free from the gravitational attraction of a massive body, such as a planet or a star

if KE = PE
no friction resistance
= escape from earths gravitational pull

Question 9

how is a satellite put into orbit

Answer 9

by accelerating it to a sufficiently high tangential speed

Question 10

what happens if satellites speed is too high?

Answer 10

it will escape

Question 11

what happens if satellites speed is too low?

Answer 11

it will return to earth

Question 12

what is Keplers 3rd law

Answer 12

the square of the orbital period of a planet is directly proportional to the cube of the seperation distance.

Question 13

what is a geostationary satellite

Answer 13

the satellite appears to remain stationary relative to a fixed point on the Earth’s surface, and it orbits the planet above the equator in the same direction as the Earth’s rotation.

Question 14

what are the two types of fields

Answer 14

radial field and uniform field

Question 15

what is gravitational field strength

Answer 15

attractive gravitational force that a unit mass would experience at a given point in the field

Question 16

GFS equation for uniform field

Answer 16

g = F/M

Question 17

GFS equation for radial field

Answer 17

g = GM/r^2

Question 18

what is gravitational potential

Answer 18

amount of work done in moving a unit mass from infinity to a given point in a gravitational field

Question 19

what is gravitational potential at infinity

Answer 19

zero

Question 20

what is the work done for gravitational potential

Answer 20

work is done to move an object closer to the field and so gravitational potential is always a negative value

Question 21

what are equipotentials

Answer 21

planes containing points with equal gravitational potential. this means that the amount of work done when an object is moved around these planes is zero

Question 22

what is a synchronous orbit

Answer 22

have a time period of one day and so return to the same place In the sky each day

Question 23

what is a low orbit?

Answer 23

orbit at heights of between 160km and 2000 km

Question 24

what is a geostationary orbit

Answer 24

have a time period of one day and stay over the same point on the earths surface,

must be directly placed above the equator and travel in same direction as earths rotation

Question 25

what is an equipotential surface?

Answer 25

a surface in which every point on the surface has the same potential

Question 26

why is the gravitational potential a negative value?

Answer 26

work needs to be done to move an object from the inside of the field to the outside

since outside the field’s potential is defined as 0 then the potential inside the field must be negative

Question 27

compare the PE and KE of a lower orbit to a higher one

Answer 27

lower orbit (smaller mass) has potential energy and more kinetic energy than a higher orbit (bigger r)