Principle of physics Measurement Measurement Chapter 1 Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.

What is physics - A way of describing the physical world - understanding the behavior and structure of matter - deals with how and why matter and energy act as they do - Evaluate explanations of physical phenomena © 2014 John Wiley & Sons, Inc. All rights reserved.

Quantities Physics © 2014 John Wiley & Sons, Inc. All rights reserved. Fundamental Quantities (Basic Quantities) quantities cannot be measured in a simpler form And for convenience they have been selected as the basic quantities. quantities that cannot be defined in any other physical quantity. The units of these quantities are called basic Units. Some quantities they have been selected as the Some quantities cannot be measured in a simpler form and for convenience they have Some Some quantities cannot The units of these are called Derived Units

Quantities Physics Table System International (SI) base quantities © 2014 John Wiley & Sons, Inc. All rights reserved. basic quantities quantity UnitSymbol length meterm mass kilogramkg time seconds electric current ampereA thermodynamic temperature kelvinK amount of substance molemol luminous intensity or (Unit of intensity of light) candelacd

© 2014 John Wiley & Sons, Inc. All rights reserved. The three main fundamental physical quantities (base quantities) of mechanics are length, mass and time. The SI system have the units meter (m), kilogram (kg), and second (S). These fundamental quantities cannot be defined in terms of more base quantities. Quantities Physics Fundamental Quantities (Basic Quantities )

Quantities Physics Fundamental unit (Basic unit) The Meter :- the distance traveled by a beam of light in a vacuum over a defined time interval ( 1/ seconds) The Kilogram :- a particular platinum-iridium cylinder kept in Sevres, France The Second :- the time interval between the vibrations in the cesium atom (1 sec = time for vibrations ) © 2014 John Wiley & Sons, Inc. All rights reserved.

Quantities Physics Fundamental unit (Basic unit) Exercise : (Homework) (SI) The Unit of Length is ……….. The Unit of Time is ……….. The Unit of Electric Current is ……….. The Unit of Temperature is ……….. The Unit of a mount of Substance is ……….. The Unit of Mass is ……….. © 2014 John Wiley & Sons, Inc. All rights reserved.

Quantities Physics Derived Quantities: All physical quantities measured by physicists can be expressed in terms of the three basic unit of length, mass, and time. When a quantity involves the measurement of 2 or more fundamental quantities it is called a Derived Quantity. The units of these are called Derived Units. © 2014 John Wiley & Sons, Inc. All rights reserved.

Quantities Physics © 2014 John Wiley & Sons, Inc. All rights reserved.

SYSTEM OF UNIT  SI units (used mostly in physics):  length: meter (m)  mass: kilogram (kg)  time: second (s) # This system is also referred to as the MKS system for meter-kilogram- second. © 2014 John Wiley & Sons, Inc. All rights reserved.

SYSTEM OF UNIT Gaussian units (used mostly in chemistry): length: centimeter (cm) cm = 0.01 m mass: gram (g) g= kg time: second (s) # This system is also referred to as the CGS system for centimeter-gram- second. © 2014 John Wiley & Sons, Inc. All rights reserved.

SYSTEM OF UNIT  British engineering system (FPS) length: foot (ft) ft = 0.30 m mass: bound bt= 0.45 kg time: second (s ) # its easy to convert from system to another. © 2014 John Wiley & Sons, Inc. All rights reserved.

CONVERSIONS You will need to be able to convert from one unit to another for the same quantity Km to m (length) J to eV (energy) Years to seconds (time) And between other systems and SI **Note: throughout you should be able to do basic conversions now and others will be developed © 2014 John Wiley & Sons, Inc. All rights reserved.

CONVERSIONS * © 2014 John Wiley & Sons, Inc. All rights reserved. 1 km = 1000 m (meters) 1kg = 1000 g 1 mile=1609 m 1g = kg 1 mile = 1.609km 1cm = 0.01 m 1 inch = 2.54 cm 1 min = 60 s 1 cm = 0.39 inch 1 hr = 3600 s 1 m 3 = 1000 L

CONVERSIONS Example : Convert 3 cm to …….inch ? Example : Convert 6 inch to ………cm ? Example : Convert 1mile to ……km ? Example : Convert 19 km to ………mile ? Example : Convert 5 mile/hr to ………. m/s ? Example : Convert 7 m/s to ………. mile/min ? Example : Convert 2 hrs to ………. s ? Example : Convert 4 min ………. hrs ? © 2014 John Wiley & Sons, Inc. All rights reserved.

Scientific notation Scientific notation employs powers of 10 to write large or small numbers Example : Convert the number to scientific notation # = ( ) # = ( ) * What is the difference between the two numbers - (4.34 x10 4 m, 43.4 x 10 3 m ) - (0.003 x s, x10 -6 s) -

© 2014 John Wiley & Sons, Inc. All rights reserved. PrefixSymbolPrefixSymbol X=18exaEdecid 15petaP-2centic 12teraT-3millim 9gigaG-6micro 6megaM-9nanon 3kiloK-12picop 2hectoh-15femtof 1decada-18attoa Power of ten prefixes :