DRAD 103 > Week 1 - Basic Physics For Radiography > Flashcards

Week 1 - Basic Physics For Radiography Flashcards

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1
Q

What are the 7 base units?

A

Energy.
Magnetic flux density.
Power.
Absorbed radiation dose.
Electric charge.
Electric potential.
Frequency.

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2
Q

How is heat a basic concept in physics of radiography?

A

Super-conducting coils of an MRI.
This generates a strong magnetic field.
Then the ceramic coil is coiled to the point where there is no resistance to electricity.
Then put in a liquid helium dewar (is very cold).

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3
Q

Part 1:
Mechanics

A
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4
Q

What is velocity?

A

It is the rate of change of position with time.

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5
Q

What is the formula for velocity?

A

Velocity = distance / time

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6
Q

What is acceleration?

A

The rate of change of velocity with time.

Objects falling to earth accelerate at a constant rate of 9.8m/s - this acceleration is due to gravity.

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7
Q

What is the formula for acceleration?

A

Final velocity - initial velocity / time

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8
Q

What are the 4 fundamental forces in nature?

A
  1. Gravity - the weakest of the 4.
  2. Weak nuclear force - the 3rd strongest.
  3. Electromagnetism - the 2nd strongest.
  4. Strong nuclear force - the strongest.
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9
Q

What is gravity?

A

The 4th strongest/the weakest fundamental forces in nature.
We only feel our weight because of the whole mass of earth acting on us.

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10
Q

What is weak nuclear force?

A

3rd strongest fundamental forces in nature.
It is important in radioactive decay (which occurs spontaneously).
It is relative to nuclear medicine.

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11
Q

What is electromagnetism?

A

Is the 2nd strongest fundamental force in nature.
This covers all electrical and magnetic phenomena.
It is a lot stronger than gravity - e.g. a fridge magnetic can stay up, working against the whole force of gravity.

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12
Q

What is a strong nuclear force?

A

This is the strongest fundamental force in nature.
The positive protons in the nucleus repel each other, and this ‘glue’ force sticks them all together - it holds the atom up.

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13
Q

What is force?

A

It’s an action that changes the motion of an object.
Can be physical (a push) or invisible (magnetism).
Its unit measurements are Newtons (N).

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14
Q

Where are forces?

A

They are repulsive forces all around, constantly, in both directions of something.

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15
Q

What is the mathematical equation for force?

A

Force = mass x acceleration
(It is newtons 2nd law -
The force applied to move an object is equal to the mass of an object multiplied by the acceleration.

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16
Q

What is Newtons 1st law?

A

No force - no acceleration -
A body at rest remains at rest, and a body in motion continues in motion until acted on by an outside force (e.g. friction).

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17
Q

What is Newtons 3rd law?

A

Action/reaction -
For every action, there is an equal and an opposite reaction.
E.g. the force of the chair your sitting on upwards is the same as the force downwards - so you stay in the same position.

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18
Q

What is weight?

A

It is the force on an object from the force of gravity.
So it can vary by location.

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19
Q

What are the unit measurements for weight?

A

Newtons (N).

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20
Q

What is mass?

A

It is the amount of matter in an object.
It is constant - doesn’t change from different surroundings.

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21
Q

What are the unit measurements for mass?

A

Kilograms (kg).

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22
Q

What is Work?

A

It is the force applied to an object x distance across which it is applied.

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23
Q

What is the formula for Work?

A

Work = force x distance

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24
Q

What are the unit measurements for work?

A

Joules (J)

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25
What is energy?
The ability to do work.
26
What are the unit measurements for energy?
Joules (J) (There is a lot of energy in 1 joule).
27
What is a joule (J)?
The work/energy required to move an object wiht the force of 1 newton over a distance of 1 metre.
28
What is power?
It is the rate of doing work.
29
What is the formula for power?
Power = work / time
30
What are the unit measurements for power?
Watts (W).
31
Power output of diagnostic imaging equipment in generators is measured in Watts.
32
What are the unit measurements for velocity?
M/s
33
What are the unit measurements for acceleration?
M/s
34
What is momentum?
It is the measure of how much motion an object has.
35
What is the formula for momentum?
Momentum = mass of the object x its velocity
36
What are the unit measurements for momentum?
Kg-m/s
37
List some different forms of energy -
GPE Kinetic Mechanical Chemical Electrical Thermal Nuclear Electromagnetic
38
What is Gravitational Potential Energy (GPE)?
It is the ability to do work because of height. By lifting an object up to a greater height, it will give it more potential energy.
39
What is the formula of GPE?
GPE = mass x gravity x height
40
What is kinetic energy?
The energy of motion.
41
What is the formula for kinetic energy?
KE = 1/2 mass x velocity
42
What is chemical energy?
It is energy released by chemical reactions. E.g. calories from food.
43
What is mechanical energy?
Air molecules compressing and expanding constantly. E.g. ultrasound, sound.
44
What is electrical energy?
Similar to GPE. It is work that can be done when electrons move through a voltage (an electrical potential difference).
45
What is thermal energy?
To do with the kinetic energy of molecules. Vibration of molecules - faster = more thermal energy = increased temperature.
46
What is electromagnetic energy?
Has many forms - all in the electromagnetic spectrum.
47
What is nuclear energy?
The energy contained in the nucleus of an atom. E.g. it is used in power plants.
48
What is conservation of energy?
It states the total amount of energy, anywhere, is constant/always remains the same. You can’t create or destroy energy, but it can change between different forms.
49
What is a transducer?
It can change one form of energy into a different form of energy. E.g. a microwave, or a lightbulb.
50
What is matter? What is its formula?
A form of energy. The formula - E = m x c squared
51
Are kinetic and potential energy linked?
Yes. The sum of them must be the same. There is high potential energy of an object at height, and as the object falls all this energy coverts onto moving kinetic energy.
52
What is heat? What are the units of measurement?
The flow of energy from one object to another. It can change the state of things, or increase somethings temperature. Measured in calories.
53
X-ray tube and heat -
Lots of heat is generated in an x-ray tube. Most energy put into the tube comes out as heat (99%). So there are ways the reduce and manage this heat so that it is less of a hazard - convection, conduction, and radiation.
54
Ways to manage heat in an x-ray tube - 1. Conduction -
This is the transfer of heat through a material - so objects need to be in contact. It is it do with trying to equalise temperatures of materials. Hotter molecules will bump into still/less vibrating molecules, making them vibrate more too (it is a transfer of kinetic energy due to collision of atoms).
55
What material is a good conductor of heat?
Metals, e.g. copper.
56
What can change the rate of conduction?
1. The area of the object (bigger = faster rate of conduction). 2. The ability of the material to conduct heat (good conductor = faster rate of conduction). 3. The temperature difference between the materials (bigger difference = faster rate of conduction).
57
Ways to manage heat in an x-ray tube - 2. Convection -
This is to do with the physical mixing of fluids, which circulates molecules all around. This means high kinetic molecules combine with low kinetic molecules. This equally distributes kinetic energy = equalises temperature.
58
Ways to manage heat in an x-ray tube - 3. Thermal radiation -
This is the transfer of heat by the emission of infrared radiation. E.g. electromagnetic waves travelling through space. It creates a reddish glow of radiation. This is the main mechanism of how an x-ray tube cools down.
59
What is the cathode in an x-ray tube?
It is negative. It is like a coil filament which heats up and glows white hot.
60
What happens once the cathode heats up a lot?
Electrons jump off its, and accelerate across the gap, due to a large potential difference, and hit into the anode.
61
What is potential difference measured in?
K.V (Kilovolts). This is able to be changed - it affects image quality and dose.
62
What is the anode?
The positive one. It is like a big metal plate.
63
What does the kinetic energy of the electrons convert into as they hit the anode?
Mostly heat (99%). X-Rays (1%).
64
What are the 7 basic quantity units?
1. Metre - M - quantity is length. 2. Kilogram - Kg - quantity is mass. 3. Second - s - quantity is time. 4. Ampere - A - quantity is electrical current (measures the flow of electrons). 5. Kelvin - K - temperature (cabin measure heat in x-ray tube). 6. Mole - Mol - amount of a substance (e.g. of pharmaceuticals). 7. Candela - cd - luminous intensity.
65
What are the secondary quantities - derived from the basic quantities?
1. Velocity - d/t, m/s 2. Acceleration - Vf - Vo /t, m/s 3. Force - m x a, N 4. Work - f x d, J 5. Power - work/t, W
66
How does energy relate to radiography?
The conversion of kinetic energy to x-rays and heat.
67
How does power relate to radiography?
The output of an x-ray generator.
68
How does electric current relate to radiography?
Measures the quantity of electrons flowing through an x-ray electrical circuit (mA).
69
How does electric charge relate to radiography?
The amount of electron charge stored on the cathode (Coulombs).
70
How does electrical potential relate to radiography?
Is what moves the electrons across the x-ray tube in the conductive material. It is the ability to do work on the electrons. Voltage (V).
71
How does magnetic flux density relate to radiography?
It is a measure of the magnets strength in the X-ray tube. It also is very important in MRInfield strength. Tesla (T).
72
How does absorbed radiation dose relate to radiography?
This is the energy put into a body of mass of 1kg by ionising radiation. Grays.
73
How does effective radiation dose relate to radiography?
Takes into account how sensitive different tissues are to harm from radiation. Measures the biological effect of the radiation. Sv.
74
What are prefixes?
The x10 the th power of …. Are used to describe very large or very small numbers. For large numbers, you need to multiply that number. For small numbers, you need to divide the number.
75
How to work with powers?
Multiplication of powers - just add the powers together. Division of powers - take away the powers from each other.
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