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Physics A2 > Gravitational And Electic Fields > Flashcards

Gravitational And Electic Fields Flashcards

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1
Q

Define force field

A

A region in which a body experiences a non contact force

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2
Q

Define gravitational force

A

A region in which a body with mass experiences a non contact force

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3
Q

Is a force field a vector or scalar quantity?

A

Vector

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4
Q

What is the inverse square law in relation to gravitational field lines

A

No of field lines in a given area is inversely proportional to the distance squared

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5
Q

What is Newton’s law of gravitation?

A

The force between 2 masses is proportional to the product of their masses and inversely proportional to the distance between them squared

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6
Q

Define gravitational field strength

What is the unit?

Is it scalar or vector?

A

Force per unit mass

Nkm-1

Vector

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7
Q

What is the equation for potential energy

In a uniform field?

In a radial field?

A

Ep = mg x change in h

Ep = - G m1 m2
———-
r

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8
Q

Define gravitational potential

What is the unit?

Is it scalar or vector?

A

The work done per unit mass in moving a body from infinity to that particular point in a gravitational field

Jkg-1

Scalar

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9
Q

Gravitational potential difference

A

The energy needed to move a unit mass between 2 points in a gravitational field

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10
Q

What is a line of equipotential?

A

A line that joins all points where V is constant

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11
Q

Why is gravitational potential negative?

A

V or Ep is taken as zero
Because work is done (per unit mass if it is V)
By the mass to move it from infinity to that particular point

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12
Q

What is the centripetal force acting on a satellite?

A

Gravitational force

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13
Q

Define orbital time period

A

The time taken for a satellite to make one orbit

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14
Q

Describe a circular orbit

What affect does it have on energy?

A

Speed and distance above mass is constant
Total energy is constant
No energy change

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15
Q

Describe an elliptical orbit

What affect does it have on energy?

A

As speed increases, radius decreases
Kinetic energy increases as potential energy decreases
Total energy is constant

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16
Q

Define escape velocity

A

The speed at which an unpowered satellite must be traveling at to escape the gravitational field of a planet

17
Q

Synchronous orbit

A

Orbiting object has an orbital period that is equal to the rotational period of the planet

18
Q

Describe a geostationary satellite

5 points

A 
It's orbit is in plane of the equator 
Time period = 24 hours 
Same fixed position relative to surface of the earth 
Orbital radius = 42 000 km
Equatorial orbit
19
Q

Define low orbiting

What is a low orbiting satellite used for?

A

A satellite which orbits between 180-2000 km above earth

Used for imaging and weather monitoring

20
Q

What are the advantages and disadvantages of a low orbiting satellite?

A

Advantages

  • cheaper
  • less powerful transmitter required because it has a small orbital radius which is useful for communications

Disadvantages
- high orbital speed and proximity so multiple satellites are required to maintain constant coverage

21
Q

Define electric field

A

A region in which a body with charge experiences a non- contact force

22
Q

What is Coulomb’s law

A

The force between 2 point charges is proportional to the product of their charges and inversely proportional to the distance between them squared

23
Q

Define electric field strength

What is the unit? (2 possibilities)

A

Force per unit charge

NC-1
Vm-1

24
Q

What is the definition for potential energy in

Uniform electric fields?

Radial electric fields?

A

Ep = VQ

Ep = +- k Q1 Q2
———
r

25
Q

Define electric potential

A

The work done per unit charge in moving a body from infinity to that particular point in an electric field

26
Q

Define electric potential difference

A

The energy needed to move a unit charge between 2 points in an electric field with different absolute electric potentials

27
Q

What does the gradient at a tangent to an electric V - r graph tell you?

A

Energy

28
Q

Why is no work done when a satellite is in orbit and is moving on the equipotential lines?

A

Work = force x distance moved in direction of force

Force is perpendicular to displacement

So no movement in direction of force, hence no work is done

29
Q

Advantages of geostationary satellite

A

Uninterrupted communication between transmitter and receiver

Steerable fish not necessary

Physics A2 (11 decks)

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