Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A Level Physics > C18 (Gravitational Fields) > Flashcards

C18 (Gravitational Fields) Flashcards

1
Q

Gravity

A

Universal attraction between any two masses
(Relatively weak force, only noticeable when one of masses very large, but also present tiny scale)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the gravitational pull excreted on a n object directly proportional to?

A

The mass

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Weight

A

Force due to gravity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Gravitational force (equation)

A

Fg=W

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Gravitational Field

A

Vol that gravity will act in

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Gravitational field strengths equal to what:

A

Gravity
W=mg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Gravitational potential energy

A

Change GPE= mg x change h

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

‘G’-Universal

A

Same throughout universe
G, very small, only significant when at least on mass is very large

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Why does the gravity equation contain a negative sign?

A

Indicates that force is attractive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What does the lines in the gravitational field indicate?

A

Direction of Fgrav would act on test mass

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Test mass

A

Mass, small enough to not have no affect on shape of field with its own gravity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

The more lines per area (gravitational field):

A

The stronger the field

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How can you detect very small changes in gravity

A

Gravimeter
Used map tunnels, caves, change volcanic activity and minerals for mining

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

For object moving in a circle, what’s it’s resultant force called

A

The centripetal force

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Centripetal force provided by…

A

Gravitational attraction of M (large body)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Centripetal force is equal to…

A

Gravitational force
Fc=Fg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Kepler’s first law

A

The orbit of every planet is an ellipse with the sun at one of the foci.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Perihelion

A

Closet distance to sun

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Aphelion

A

Furthest distance from sun

20
Q

Eccentricity

A

Measure of how elongated the circle is (usually orbits have low eccentricity).

21
Q

Kepler’s second law

A

A line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time

22
Q

As planets move on their elliptical orbit their speed….

A

Isn’t constant
When closer they travel faster

23
Q

Kepler’s third law

A

The square of the orbital period (T) of a planet is directly proportional to the cube of its average distance (r) from the Sun

24
Q

The gradient of a graph with T squared against r cubed is…

A

4Pi^2 / GM

25
Q

Satellite

A

Body that circles round another body in space

26
Q

Give examples of natural satellites

A

Moons
Stars
Comets
Asteroids
Planets

27
Q

Uses of satellites

A

Communication (satellite phones, not mobile phones, TV, some types of satellite radio)

Military (reconnaissance)

Scientific research (Study universe and monitor Earth, population crops vegetation)

Weather and Climate: (Predicting and monitoring weather across the globe and monitoring long term changes in climate)

Global positioning

28
Q

Stallites orbiting Earth obey what laws

A

Kepler’s laws

29
Q

What provides the centripetal force on each satellite

A

Gravitational force between it and the Earth

30
Q

Why don’t the satellites fall towards earth if the only force acting upon them is Fg

A

Always falling,however travels great distance, that as it falls Earth curves away beneath it, keeping it the same height.

31
Q

What is required for a stable orbit

A

Exactly right height and speed

32
Q

The correct speed for stable orbit at distance r from centre mass of Earth is given by…

A

V=✓Gm/r

33
Q

What does every satellite that is placed in a given orbit at a given height have in common

A

They all travel at the same speed (even if their masses vary)

34
Q

Once launched they’re normally above atmosphere, where there’s no air resistance meaning…

A

No air resistance to slow them down, as a result they travel at a constant speed

35
Q

Polar orbits

A

Circle poles
Offers complete view Earth, over given period, as Earth rotates beneath, satellites covers all parts globe after number of orbits, useful for mapping and reconnaissance

36
Q

Low Orbit

A

Satellites in orbit close to Earth, Kepler’s third law (T squared directly proportional to r cubed)
Only short time taken to orbit Earth

37
Q

Geostationary satellites

A

Placed in orbit above equator
As height increases T increases = can choose it’s T by altering height

Geostationary placed in specific orbit, so remains above same point of Earth whilst it rotates

38
Q

To be in a geostationary orbit satellite must…

A

Be in orbit above Equator
Rotate same direction as Earth
Have orbital period, 24hrs

39
Q

The orbital period of geostationary satellites is how long?

A

24hrs

40
Q

Gravitational potential (definition):

A

The potential energy per kg, at any in the field. 0 potential is defined at infinity, so point close to a mass , potential of any object would be -ve.

41
Q

Gravitational potential energy (definition):

A

The work done per unit mass in moving object from infinity to a point in the field.

42
Q

Escape velocity (definition), and where is the equation derived from?

A

Min V required to escape gravitational field strength of an object (when projected vertically from the surface).

Derived by equation 1/2 mv^2 = GMm / r

43
Q

Fc = Fg
If Fc = mv^2 / r
And Fg = -GMm / r^2
Then what can be stated?

A

m = rv^2 / G

44
Q

What’s the equation for V (stable velocity)?

A

V = square root ( GM / r )

45
Q

Equation for change in Grav potential energy;

A

Change Ep = m x g x change h

46
Q

How do you prove the T^2 is directly proportional to r^3

A

T=d / v
T= 2pi x r / v
T^2 = 4pi^2 x r^2 / v^2

v^2 = MG / r

T^2 = 4pi^2 x r^3 / MG

A Level Physics (28 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions