االولى المحاضرةPhysics and Measurement

physical quantities are:1 -basic quantities: length, mass, and time

2 -derived quantities, in that they can be expressed as combinations of a small number of basic quantities.

International system for units (SI):SI units of length (L) is meter (m)SI units of mass (M) is kilogram (Kg)

SI units of time (T) is second (s)

Standards of Length, Mass, and Time

Matter and Model Building

Atoms consists of: 1 -protons : carry a positive electric charge.2 -electrons: carry a negative electric charge

3 -Neutrons: has no chargeAtomic number: the number of protons in its nucleus. (does not vary)mass number: defined as the number of protons plus neutrons in a nucleus. (vary)

Example (1):

Density and Atomic Mass

Density is:1 -a derived quantity .

The density of any substance is defined as 2- mass per unit volume:

3 -density SI unit is Kg/m3

4 -density is a property of material.Example: aluminum has a density of 2.70 g/cm3

Atomic mass:

measured in atomic mass units (u):

Density and Atomic Mass

Quick Quiz (1)

Example 1.1

Problem 1.3

Dimensional Analysis

-The word dimension denotes the physical nature of a quantity.

- brackets [ ] dimensions of a physical quantity.

Example:

A distance is measured in units of feet or meters still a distance .

distance dimension is length.

or ; [distance ] = L

Examples: 1- dimensions of speed v are written [v] = L/T.

2- the dimensions of area A are [A] = L2

3- The dimensions and units of area, volume,

speed, and acceleration are listed in Table:

Dimensional Analysis

Dimensional analysis

. Dimensions can be treated as algebraic quantities.

(quantities can be added or subtracted only if they have the same dimensions).

. The dimensional form of the equation:

is

Quick Quiz

Example

Example 1.3

QUESTIONS

QUESTIONS

QUESTION (3)

Conversion of Units

convert units from one measurement system to another.

Example: convert 15 cm to meters:

m

cm

mcm 15.0

100

11515

Example

Example

Example

Example

Example

Exercises