Brainscape's Knowledge GenomeTM

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


See full index

Z A Level Physics 2 > Gravitation > Flashcards

Gravitation Flashcards

You may prefer our related Brainscape-certified flashcards:
Physics 101 flashcards AP® Physics flashcards
1
Q

What is a force field and what is an example of one?

A
  1. A force filed is a region where an object will experience a non-contact force
  2. Force fields cause interactions between objects or particles e.g. between static or moving charges, or in the case of gravity, between masses
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is Newton’s law of attraction?

A

F = Gm1m2 / r2

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

What can Newton’s law be used to calculate?

A
  1. The force between two point masses
  2. The force between a planet and a small mass
  3. The force between two planets or stars
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What happens when a mass is placed in a gravitational field?

A

Any object with mass will experience an attractive force if you put it in the gravitational filled of another object

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

How does gravity change?

A
  1. On Earth gravity exerts a larger force on more massive objects
  2. The moon has a smaller surface gravity than the Earth because it is a less massive body
  3. A planet’s pull of gravity gets weaker further away from that planet’s surface
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is G?

A

The universal constant of gravitation, 6.67x10^-11 Nm^2kg^-2

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

What is the inverse square law?

A

1/r2

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

What is gravitational field?

A

A region in space in which a massive object experience a gravitational force

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

What is field strength?

A

The strength of the gravitational field measured in Nkg^-1

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

What do field lines represent?

A
  • The direction of the gravitational force on an object and strength of the field
  • The spacing of the lines gives a measure of field strength
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the gravitational field strength defined as?

A

g = F/m (gravitational force, N), (mass, kg)

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

What is the gravitational field like near the surface of a planet?

A
  • The gravitational field is very early uniform

- This means that the field is one of the same strength and direction everywhere

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

What is the shape of the field near to the Earth? What does this mean?

A
  • Radial field

- Here the field lines all point to the centre of the planet

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

Why can you still use Newton’s law of gravity to calculate the gravitational forces between two planets?

A

The field is exactly the same shape as it would have been if all the mass of the planet were concentrated at its centre

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

How does gravitational field strength change?

A

The gravitation field strength DECREASES in strength with increasing distance from the centre of the planet

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

What is another equation for gravitational field strength?

A

g=GM/r^2

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

How do you calculate gravitational potential energy?

A

mgh

18
Q

What is gravitational potential difference?

A
  • The gravitational energy difference per kilogram
  • Gravitational potential and potential difference have unit Jkg-1
  • Gravitational potential is given the symbol V, and the gravitational potential difference is given the symbol deltaV
19
Q

How do you calculate gravitational potential difference?

A

DeltaV = gDeltah

20
Q

What happens when an object moves along an equipotential line?

A

The potential energy (and therefore the potential) stays the same

21
Q

What are equipotential surfaces?

A
  • They are always at right angles to the gravitational field
  • When something moves at right angles to the field (and hence along the equipotential) NO WORK IS DONE by or against the filed, so there is NO potential energy change
  • When something moves along a field line, there is a change of gravitational potential energy
22
Q

How is gravitational field linked to the gravitational potential gradient? Why is there a minus sign?

A

g = -DeltaV / Deltah
-The significance of the minus sign is that the potential gradient deltaV/deltah is in a positive direction upwards, because the potential increases as the height above the planet increases. The gravitational field direction is downwards

23
Q

How does the gravitational force on an object of mass m change near to planet of mass M?

A
  • The graph shows that a force F, acts not he object at. distance r form the centre of the planet
  • If the object is moved a small distance, or further away from the planet, we can calculate the increase, in the objects GPE
  • DeltaEp = work done = fr
24
Q

Why is fdeltar more usually written as mgdeltah?

A

Because the force acting on the mass is equal to it weight, mg

25
Q

How do you calculate the change in potential energy?

A

DeltaEp = GMm [1/r1 - 1/r2]

26
Q

What is the increase in potential, deltaV?

A

DeltaEp/m

-This allows use to think about defining gravitational potential close to a planet

27
Q

What is the potential change moving r1 to infinity?

A

DeltaV = GM/r1

28
Q

What is the potential at a distance r from the centre of a planet of mass M?

A

V = -GM/r

29
Q

How does the potential gradient change?

A
  1. The potential gradient is steep closer to the planet’s surface
  2. The filed lines are closer together near the surface, because the gravitational field strength, g, is stronger
    - These tow statements ar blinkend through g= -deltaV / deltah or g=-deltav/deltar
    - These are the same but deltah has been used for a change in height and delta has been used for a change in distance from the centre of a planet
30
Q

Why does the Earth has an atmosphere?

A

-The molecules of gas moving in our atmosphere do not have enough kinetic energy to escape the pull of gravity at the Earth’s surface

31
Q

What happens when a fast moving object leaves the surface of a planet?

A
  • The decrease in kinetic energy os equal to the increase in gravitational potential
  • This assume that the object is NOT affected by an atmosphere and is in free fall (this is not a spacecraft with a rocket)
32
Q

What happens when a n object is is about to just escape the pull of the planet?

A

Ke1 - Ke2 = mdelatV

-Its speed V2, will kist reach zero at an infinite distance from the planet

33
Q

What is escape velocity?

A

The minimum velocity an object mist have at the surface of a planet to escape the pull of gravity using its own kinetic energy

34
Q

What does the pull of gravity do in relation to the circular motion?

A

The pull of gravity provides the necessary centripetal force to keep the planet in orbit

35
Q

How do you work out the velocity of an orbit? What does it tell you?

A

V^2 = GM/r

-The speed of the orbit is faster for small orbits

36
Q

How do you link the time period of an orbit to the radius of the orbit?

A

-The speed of the orbit is linked to the circumference @pir and the time period, T of the orbit through the equation:
V = wr = 2pir / T
T^2 = (4pi^2 / GM) r^3

37
Q

What are the different orbits?

A
  • Most orbits have an elliptical shape
  • Most planetary orbits are nearly circular
  • However comets, some minor planets have elongated (or eccentric) elliptical orbits
  • The Sun’s solar wind always blows the comets tail away from the sun
38
Q

Describe the motion of an elliptical orbit A to D, starting at A nearest the Sun

A
  • When a planet or comet moves in an elliptical orbit, its speed changes, but the total energy of the body stays the same
  • A: comest moves at fastest orbital speed, but smallest GPE because ti is closest to the Sun
  • B: component of the Sun’s gravitational pull on the comet which slows it down
  • C: It is at its furtherest point form the sun and it has its lowest KE at this point but highest GPE
  • D: The comet is falling back towards the Sun, there is a component of the Sun’s gravitational pull, which speeds it ip. The comets potential energy is being transferred into KE, and the comet reaches it maximum speed again at A
39
Q

How are satellite orbits use?

A
  • Satellites are in orbit around the Earth (for communications and observations)
  • Low orbit: able to take photos of world below
  • High orbit: useful for communication because messages may be sent form one part of the world to another via the satellite
40
Q

Whta is a geosynchronous orbit?

A
  • In this case the satellite is placed in orbit above the Earth;s equator, at such a height that it takes exactly one day to complete an orbit
  • The orbit is synchronised with the Earth’s rotation, so that it remains in the same place above the Earth’s surface
  • This means that our satellite dishes e.g. can be aligned with a satellite which always lies in the same position relative to Earth
41
Q

State Newton’s law of gravitation

A
  • Forces of attraction between two point masses
  • Is proportional to the product of the masses
  • Inversely proportional to the square of the distance between them

Z A Level Physics 2 (16 decks)

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