gravitational fields

Question 1

what is a gravitational field

Answer 1

is the region around a body in which other bodies of mass will experience a force.

Question 2

gravitational field lines

Answer 2

show the shape of the field and the direction of the field

Question 3

what is the gravitational field strength

Answer 3

at any point in the gravitational field strength is the force acting per unit mass as that point, g=F/m

Question 4

what type of quantity is gravitational field

Answer 4

vector

Question 5

are gravitational fields attractive or repulsive

Answer 5

attractive

Question 6

what happens when we measure the gravitational field strength when we double the distance

Answer 6

will have quarter the strength. inverse square

Question 7

what is newtons law of gravitation

Answer 7

the relationship between the gravitational force between two bodies is directly proportional to the masses and inversely proportional to the distance.

Question 8

what is the equation known as newtons law of graviton

Answer 8

F=-GMm/r^2

Question 9

what is the gravitational constant

Answer 9

G=6.67x10^-11 Nm^2kg^-2

Question 10

Two masses M and 4M, how does this effect a force

Answer 10

4F

Question 11

sub in g=f/m into F=-GMm/r^2

Answer 11

g=-GMm/mr^2

g=-GM/r^2

Question 12

what is the variation of g from the earths surface outwards

Answer 12

g=-GM/(R+h)^2

Question 13

what is kepler’s third law

Answer 13

states that the square of the period of the planet orbiting the sun is proportional to the mean radius of its orbit cubed: t^2∝r^3

Question 14

geostationary orbit

Answer 14

is an orbit of the earth made by a satellite that has the same time period and orbital direction as the rotation of the earth.

Question 15

what is kepler’s laws

Answer 15

1. planets travel around the sun in elliptical orbits
2. a line joining the sun to a planet will sweep out areas in equal time
3. the time period squared to orbit the sun will be proportional to the radius cubed

Question 16

explain this equation T^2=(4π^2/GM)r^3

Answer 16

F=-GMm/r^2
mv^2/r=GMm/r^2
sub in 2π/T
T^2=(4π^2/GM)r^3

Question 17

what are geostationary satellites used for

Answer 17

broadcasting
monitoring the weather
monitoring traffic

Question 18

what is gravitational potential

Answer 18

defined as the work done in moving a mass from infinity
the unit jkg^-1

Question 19

what is the gravitational potential energy

Answer 19

gpe of a mass in a gravitational field depends on its position in the field.

Question 20

the escape velocity

Answer 20

escape velocity from a point in a gravitational field is the minimum launch velocity required to move an object from that point to infinity.

Question 21

variation of gravitational potential with distance for a radial field.

Answer 21

v=-GM/r

Question 22

how do you work out gravitational potential

Answer 22

v=-GM/r

Question 23

Calculate the gravitational potential energy

Answer 23

energy=-GMm/r

Question 24

why is gravitational potential always negative

Answer 24

gravity is an attractive force, moving away from infinity

Question 25

how can we convert Gravitational potential, to Gravitational Field Strength

Answer 25

by dividing by r, g=v/r

Question 26

why cant a satellite orbit the south pole

Answer 26

orbit must be equatorial. velocity of spaceship must be parallel to the velocity of a point on the surface of planet.
spaceship must orbit in the same direction as the planet.