## 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

3.Time

- What are Secondary Quantities also called?

Why? - 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

(Rem/Sievert)

4. Radioactivity

(Curie/Becquerel)

- 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?
- Cryogens.