gravitational fields

Question 1

gravitational field

Answer 1

area in which objects with mass experience a non contact force

Question 2

gravitational field strength

Answer 2

the force per unit mass exerted by a gravitational field
g=F/m

Question 3

newtons law of gravitation

Answer 3

shows that the magnitude of the gravitational force between two masses is directly proportional to the product of the masses, and is inversely proportional to the square of the distance between them
F=GMm/r^2

Question 4

gravitational field strength in a radial field

Answer 4

F=GMm/r^2 g=F/m

gm=GMm/r^2 g=GM/r^2

Question 5

gravitational potential

Answer 5

the work done per unit mass when moving an object from infinity to that point. At infinity, it is 0, and as it moves away from infinity to a point, energy is released as gravitational potential energy is reduced. therefore it is always negative

Question 6

gravitational potential difference (∆v)

Answer 6

the energy needed to move a unit mass between two points, and therefore can be used to find the work done when moving an object in a gravitational field.
workdone=m∆v

Question 7

velocity of an object with a change in Potential

Answer 7

E1-E2=0.5v^2

Question 8

similarities between electric and gravitational fields

Answer 8

-forces both follow inverse square law
-uses field lines to represent and can both be either uniform or radial
-use equations of a similar form to find the force exerted and field strength

Question 9

differences between electric and gravitational fields

Answer 9

-grav fields are always attractive, whilst electric fields can repel
-electric forces acts on charge, whilst gravity acts on mass

Question 10

orbital motion

Answer 10

Keplers third law is that the square of the orbital period is dire try proportional to the cube of the radius

derive the equation !

Question 11

gravitational potential energy

Answer 11

GPE=Gmm/r

Question 12

how to calculate a new time period if distance from the centre is changed

Answer 12

due to Keplers law T^2 is proportional to r^3, and so T1^2/T2^2=r1^3/r2^3

Question 13

kinetic energy during orbit

Answer 13

the closer the orbit to the surface, the greater the kinetic energy as it will have a greater velocity due to the shorter time period.

Question 14

geostationary orbit

Answer 14

time period of 24 hours and so stays above the same point of the equator