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Advanced Higher Physics > Rotational Motion And Astrophysics > Flashcards

Rotational Motion And Astrophysics Flashcards

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
What is the definition for apparent brightness of a star?
The amount of energy per second from the star landing normally on 1 square metre at the surface of the Earth
26
Why do high mass stars have shorter lifetimes than low mass stars?
They start with a greater supply of fuel but they use it up at a greater rate
27
Where are stars formed?
Inside relatively dense clouds of gas and dust
28
What is escape velocity defined as?
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
What does the equivalence principle state?
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
When will time run slower?
Under the influence of greater gravity
31
What is the event horizon?
The boundary between the inside of a black hole and the outside universe
32
What is the escape velocity from from the event horizon of a black hole?
Equal to the speed of light
33
The event horizon of a black hole forms a sphere. What is the radius of this sphere called?
The Schwarzschild radius
34
What is the luminosity of a star?
The total energy radiated per second by the star
35
What is the apparent brightness of a star?
The amount of energy per second from the star landing normally on 1 square metre at the surface of the Earth
36
What produces an angular acceleration?
An unbalanced torque
37
What is the unit of torque?
Nm
38
What does the angular acceleration produced by an unbalanced torque depend on?
The moment of inertia of the object
39
What does the moment of inertia of an object depend on?
The mass of the object, and the distribution of the mass about a particular axis
40
What is the angular momentum of a rigid object the product of?
Moment of inertia and angular velocity.
41
In the absence of external torques, what is the total angular momentum of a rotating rigid object before a collision equal to?
The total angular moment after impact
42
What does the rotational kinetic energy of a rigid object depend on?
Its moment of inertia and angular velocity.
43
What value does gravitational potential and gravitational potential energy have at infinity
Zero
44
What does Special Relativity deal with?
Motion in inertial (nonaccelerating) frames of reference.
45
What does General Relativity deal with?
Motion in non-inertial (accelerating) frames of reference
46
What is the Equivalence Principle?
An observer cannot tell the difference between a uniform gravitational field and a constant acceleration
47
Describe the consequences of the Equivalence Principle
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
What is spacetime a representation of?
Four dimensional space
49
What path does light or a freely moving object follow in spacetime?
A geodesic (the shortest distance between two points)
50
What does mass do to spacetime?
Curves it
51
How does gravity arise?
From the curvature of spacetime
52
What happens to time at the event horizon of a black hole?
It appears to be frozen

Advanced Higher Physics (4 decks)

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