gravitational (everything)

Question 1

what is a force field

Answer 1

a region where an object will experince a non-contact force

Question 2

force fields can be represented as ______

Answer 2

vectors

Question 3

in uniform feilds the field strenth is ______ and the field lines are _____

in radial feilds the lines ____ __ ____ _____. and gravitatinal field is ___ ______

Answer 3

uniform, parallel

meet at the center, not uniform

Question 4

newtons law of gravitation formula

Therefore F∝

Answer 4

F=GMm/r^2

inversly preportinal to r^2
F∝1/r^2

Question 5

g equation if we assume g is constent (uniform fields)

g equation of we assue g is not constent (radial fields)

unit for both

Answer 5

g = F/M

g=GM/r^2

Nkg^-1

Question 6

what value is the gravitational constent G

Answer 6

6.67x10^-11 Nm^2Kg^-2

Question 7

gravitatinal potential (v) (simple defonition) is …..

(Double check)

Answer 7

potential enegy per unit mass

Question 8

gravitatinal potential equation and unit

Answer 8

V=-GM/r

JKg^-1

Question 9

gravitatinal potential enegy is what times gravitatinal potential
(show this in equation)

Answer 9

times m (mass of second object)

gravitatinal potential V = -GM/r
gravitatinal potential enegy =GMm/r

Question 10

gravitatinal potential is 0 at ____

Answer 10

∞

Question 11

What is gravitational field stength in terms of gravitational potential and distance from centre of mass

give the equation for this

Draw this graph (v over r graph)

The graidient is….

Answer 11

force per unit mass
(use this one on most cases unless the question heavaly talks about gravitatinal potential)
OR
the rate of change of gravitational potential (v) over distence r from center of mass

g=-ΔV/Δr

See pg 122

Gradient = g

Question 12

draw g over r graph. what is the area

Answer 12

see pg 122
area = ΔV

Question 13

excape velocity is when…

thereofre derive velocity for needed for the excape velocity

Answer 13

at wich the objects Ek = - gravitatinal potential enegy

1/2 mv^2 = - - GMm/r
1/2 v^2 = GM/r
V^2 = 2GM/r
V = root2GM/r

Question 14

gravitatinal potential diffrence is…

thereofre
give the equation for work done to move a mass between 2 points in a gravitatinal feild

Answer 14

the enegy neded to move a unit of mass between 2 points in a gravitaional field
(the diffrence in gravitatinal potential bewteen the 2 ponts)

ΔWd=mΔV

Question 15

when you travel along a equapotantial you dont ____ or _____ ______

Answer 15

lose or gain enegy

Question 16

derive the fact T^2 ∝ r^3 of an object in orbit

Answer 16

F=GMm/r^2 F=mv^2/r
centrepetal force = centrepetal foce
F=F
GMm/r^2=mv^2/r
1/r=mv^2/GMm
r=GM/v^2
v^2=GM/r
v=rootGM/r

s=d/t
d=2πr
t=T
s=2πr/T

s=v
2πr/T=rootGM/r
4π^2r^2/T=GM/r
1/T=GM/4π^2r^3
T=4π^2r^3/GM
all constent exept T and r
therefore
T^2∝r^3

Question 17

orbating objects have constent total enegy consisting of __ + ____ _____

since total enegy is constent if potential enegy decreases (distence from mass (r) becomes smaller) then __ _______ meaning _____ ______

Answer 17

Ek + potantial enegy

Ek incresease, velocity increases

Question 18

geosationary orbat
distence form earths center
and
time preied

Answer 18

42000km

24hours

Question 19

LEO
distence from earth

Answer 19

below 2000Km

Question 20

ΔEk=
(For an object in orbit with constant total energy)

Answer 20

ΔGPE

Question 21

exam question (2mark):
define the gravitatinal potential enegy at a point in the gravitatianl feild

Answer 21

gravitatinal potential is the word done per a unit mass moving a unit mass from from ∞ to that point

Question 22

some characteristics of lower poler orbit (3)

Answer 22

• orbiting height is low (below 2000Km)
  thereofre lower signal strenth requierd
• can collect data from regions inexessible to man
• contact with revever is intemitent

Question 23

some characteristics of geosyncrinyis orbat above equator (4)

Answer 23

-maintains same position reletive to earth (T=24hours)obit
- hight is high (42000Km)
- sacns a resticted and fixed area of the earth only
- arial can be in a fixed position

Question 24

exam question (2mark):
define gravitational feild strenth and define weather it is a vector or a scaler

Answer 24

• g is force per unit mass
• g is a vector quantity

Question 25

exam question (1mark):
state what is represented by gravitaional field lines

Answer 25

they show the direction of force and the reletive magnatude a mass will experince within a gravitational field

Question 26

equapotential lines cross…

Answer 26

field lines at 90 degrees

Question 27

what is the Ek of an object in orbit?
(extra equation tutur said is hlpfull to rember)

Answer 27

Ek=GMm/2R

Question 28

for an object within a circular obit:
(not a needed derivation but may help):
V(velocity) ∝ (includes r)

derive it

Answer 28

1/root r

F=F
mv^2/r=GMm/r^2
v^2=GM/r
v=rootGM/r
therefore
v=root1/r