Glossary of RadTech: Physics - Ch.3

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Give a definition of Physics.
Physics is the study of the interaction of matter and energy in all their forms.
In Mechanics what three measurable quantities are considered Basic?
1. Mass

2. Length

What are Secondary Quantities also called?

Derived Quantities.

They are derived from combinations of the Basic Quantities.
What are Special Quantities?
They are Quantities that support measurement in specialized areas of science.
Give four Special Quantities used in Radiology.
1. Exposure
(Roentgens/Air Kerma)

2. Dose (
(Rad/ Gray)

3. Effective Dose

4. Radioactivity
Give four systems of units.
1. SI -System Internationale

2. MKS -Meter-Kilogram-Second

3. CGS -Centimeter-Gram-Second

4. British -Foot-Pound-Second
What are the SI and British units of Length?

What is their relation?
1. Meters: 1m = 3.28f

2. Feet: 1f = .3m
How is the meter defined?
The distance traveled by light in 3 x 10⁻⁹ seconds.
What is the SI unit of Mass?

How does it differ from the British unit?
1. Kilogram

2. The British Pound is a unit of Weight (Gravity acting on it)
What is the SI & British unit of Time?

What is it based on?
1. The Second

2. It is based on the vibrations of Cesium (Ce) atoms.
What is the definition of Mechanics?
A segment of Physics that deals with objects at rest (Statics) and objects in motion (Dynamics).
What is the definition of Velocity.

What is its formula?
The rate of change of Position with time.

v = d/t
What is the formula for Average velocity?
v⁻ = (vo + vf)/2
What is the definition of Acceleration?

What is its equation?
The rate of change of Velocity with Time.

a = (vf -Vo)/t
What is Newton's First Law?
A body will remain at rest or continue to move with constant velocity in a straight line unless acted upon by an external force.
What is another name for Newton's First law?

How is this new term defined?
The Law of Inertia.

The property of matter that acts to resist a change in its state of motion.
What is Newton's Second Law?

What is its equation?
The Force (F) acting on an object with Acceleration (a) is equal to the product of its Mass (m) and the Acceleration produced by the Force.

F = ma
What is the SI unit of Force?
The Newton
What is Newton's Third Law?
For every Action there is an equal and opposite Reaction.
Define Weight.

What are the SI and British units for the Constant now introduced?
Weight (Wt) is the Force on a body caused by the downward pull of Gravity on it.

SI: g = 9.8m/sec/sec

British: g = 32ft/sec/sec
What is the equation for Weight?

What is the equivalence between SI and British units.
Wt = mg

1 lb = 4.5 Newtons
Define Momentum.

What is its equation?
Momentum is the product of a body's mass (m) and its velocity (v).

p =mv
Define Work.

What is its equation?

What is its Unit?
Work (W) is the product of the Force (F) applied and the Distance (d) over which it is applied.

W = Fd Joules (J)
Define Power.

What is its equation?

What is its Unit?
Power (P) is the rate of doing Work
Or: Power is the quotient of work by Time.

P = Fd watts (W)
= mad
State the Law of Conservation of Energy.

How is energy defined?
Energy cannot be created or destroyed but can be transformed from one form to another.

Energy is the capacity to do work.
What are the two forms of Mechanical Energy?

How are they defined?
Kinetic Energy (KE): Energy by virtue of the motion of an object.

Potential Energy (PE): Energy by virtue of an object's position.
What are the two equations for energy?
KE = 1/2(mv2)

PE = mgh

(h is height above the earth's surface)
How is Heat defined?

What is its Unit?
Heat is the kinetic energy of the random motion of molecules.

The Calorie
If one object has more heat than another what can be said about it?
The motion of its molecules are more rapid and disordered than the other's.
How can heat be transferred?
1. Convection

2. Conduction.

3. Radiation.
Define Conduction.
The transfer of heat through a material, or by touching.
Define Convection.
The mechanical transfer of heat by movement of 'hot' molecules in a gas or liquid from one place to another.
Define Radiation (of Heat)
Thermal Radiation is the transfer of heat by the emission of infra-red radiation.
Define Temperature.
a. The degree of hotness or coldness of a body or environment.

b. A measure of the average kinetic energy of the particles in a sample of matter, expressed in terms of units or degrees designated on a standard scale.
What are Scalar and Vector quantities?
Scalar: refers to a quantity, such as mass, length, or speed, that is completely specified by its magnitude and has no direction.

Vector: refers to a quantity, such as velocity, that is completely specified by a magnitude and a direction.
What are the three types of temperature scale?
1. Celsius (c)

2. Fahrenheit (f)

3. Kelvin (k)
What is the equation to convert Fahrenheit to Celsius?
Tc = 5/9(Tf-32)
What is the equation to convert Celsius to Fahrenheit?
Tf = 9Tc/5 + 2
What is the equation to convert Celsius to Kelvin?
Tk = Tc + 273
What is the word for extremely cold liquids?

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