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Advanced Higher Physics > Rotational Motion And Astrophysics > Flashcards

Rotational Motion And Astrophysics Flashcards

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1
Q

What is the angular velocity of a rotating object defined as?

A

The rate of change of angular displacement or the change in angular displacement per unit time

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2
Q

What is angular acceleration defined as?

A

The rate of change of angular velocity

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3
Q

Wgat is tangential acceleration defined as?

A

The rate of change of tangential or linear velocity

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4
Q

What is centripital acceleration defined as?

A

The rate of change in linear velocity

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5
Q

What direction is centripital acceleration always towards?

A

The centre of the cirlce

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6
Q

What is centripital acceleration always at a right angle to?

A

The tangential acceleration

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7
Q

What is torque defined as?

A

The product of radius and force applied at that radius to an axis of rotation.

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8
Q

What is the moment of inertia of a mass defined as?

A

A measure of its resistance to angular acceleration about a given axis.

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9
Q

When is angular momentum conserved?

A

When two or more objects collide in the absence of external torques

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10
Q

What happens when torque does work on a body to make it rotate?

A

It gains kinetic energy

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11
Q

What is gravitational field strength defined as?

A

The force per unit mass at a point.

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12
Q

How are satellites held in orbit around the Earth?

A

It is as a consequence of the Earth’s gravitational force which provides a centripetal force on the satellite.

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13
Q

What is gravitational potential at a point in space defined as?

A

The work done by external forces to move unit mass from infinity to that point

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14
Q

What is the value of both gravitational potential and gravitational potential energy at infinity?

A

Zero

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15
Q

What is gravitational potential proportional to?

A

1/r

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16
Q

What is gravitational force proportional to?

A

1/r^2

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17
Q

What is step 3 of the proton-proton chain?

A

Two helium-3 nuclei fuse to form helium-4

Two protons are released at the same time

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18
Q

What is step 2 of the proton-proton chain?

A

The deuterium nucleus fuses with a proton to produce helium-3
A gamma ray is released as the same time
This happens twice

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19
Q

What is step 1 of the proton-proton chain?

A

Two hydrogen nuclei (protons) combine to form a deuterium nucleus
A positron and a neutrino are released at the same time
This happens twice

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20
Q

What are the axis on the Hertzsprung-Russel diagram?

A 
x = Surface temperature (K)
y = Luminosity
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21
Q

What are the groups called in the Hertzsung-Russel diagram?

A

Main sequences
Giants
Supergiants
White dwarfs

22
Q

What is the formula for the apparent brightness of a star?

A 
b = L/4πr^2
b = Apparent brightness
L = Luminosity
r = Distance from Earth
23
Q

What is the equation for the luminosity of a star?

A 
L = 4πr^2σT^4
L = Luminosity
r = Radius
T = Surface temperature
24
Q

What is the definition for luminosity?

A

The total energy radiated per second by the star

25
Q

What is the definition for apparent brightness of a star?

A

The amount of energy per second from the star landing normally on 1 square metre at the surface of the Earth

26
Q

Why do high mass stars have shorter lifetimes than low mass stars?

A

They start with a greater supply of fuel but they use it up at a greater rate

27
Q

Where are stars formed?

A

Inside relatively dense clouds of gas and dust

28
Q

What is escape velocity defined as?

A

The minimum velocity required to allow a mass to escape a gravitational field, achieving zero kinetic energy and maximum (zero) gravitational potential energy at infinity

29
Q

What does the equivalence principle state?

A

No observer can determine by experiment whether they are in an accelerating frame of reference or in a gravtational field. The laws of physocs cannot be distinguished between acceleration and gravity

30
Q

When will time run slower?

A

Under the influence of greater gravity

31
Q

What is the event horizon?

A

The boundary between the inside of a black hole and the outside universe

32
Q

What is the escape velocity from from the event horizon of a black hole?

A

Equal to the speed of light

33
Q

The event horizon of a black hole forms a sphere. What is the radius of this sphere called?

A

The Schwarzschild radius

34
Q

What is the luminosity of a star?

A

The total energy radiated per second by the star

35
Q

What is the apparent brightness of a star?

A

The amount of energy per second from the star landing normally on 1 square metre at the surface of the Earth

36
Q

What produces an angular acceleration?

A

An unbalanced torque

37
Q

What is the unit of torque?

A

Nm

38
Q

What does the angular acceleration produced by an unbalanced torque depend on?

A

The moment of inertia of the object

39
Q

What does the moment of inertia of an object depend on?

A

The mass of the object, and the distribution of the mass about a particular axis

40
Q

What is the angular momentum of a rigid object the product of?

A

Moment of inertia and angular velocity.

41
Q

In the absence of external torques, what is the total angular momentum of a rotating rigid object before a collision equal to?

A

The total angular moment after impact

42
Q

What does the rotational kinetic energy of a rigid object depend on?

A

Its moment of inertia and angular velocity.

43
Q

What value does gravitational potential and gravitational potential energy have at infinity

A

Zero

44
Q

What does Special Relativity deal with?

A

Motion in inertial (nonaccelerating) frames of reference.

45
Q

What does General Relativity deal with?

A

Motion in non-inertial (accelerating) frames of reference

46
Q

What is the Equivalence Principle?

A

An observer cannot tell the difference between a uniform gravitational field and a constant acceleration

47
Q

Describe the consequences of the Equivalence Principle

A

Clocks in non-inertial reference frames e.g. accelerating spacecraft 
Clocks at altitude i.e. clocks run at different speeds in different gravitational field strengths 
Precession of Mercury’s orbit 
Gravitational lensing of light

48
Q

What is spacetime a representation of?

A

Four dimensional space

49
Q

What path does light or a freely moving object follow in spacetime?

A

A geodesic (the shortest distance between two points)

50
Q

What does mass do to spacetime?

A

Curves it

51
Q

How does gravity arise?

A

From the curvature of spacetime

52
Q

What happens to time at the event horizon of a black hole?

A

It appears to be frozen

Advanced Higher Physics (4 decks)

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