Physical World And Measurement What is physics? Physics is that branch of science in which we study about nature and natural phenomenon Branch Of Physics 1- Mechanics Motion of object at low speed 2- Thermodynamics Theory of heat and temperature 3- Electromagnetism Electricity and magnetism 4- Relativity Motion of high speed moving particles 5- Quantum Mechanics Some microscopic particles 6- Technology Application of science for practical purpose

3- Strong force 4- Weak force Basic Forces In Nature Acts with in the neucles up to distance 10-5 . It is attractive and short ranged. 4- Weak force Decay of neutron

Nature of physical laws To understand types of motion Law of conservation of momentum Newton’s second law I If no force is acting on a body momentum remains constant . II If no force acting on a body angular mom. Remains constant . Law of conservation of Energy Energy can neither be created nor destroy. But can change from one form to another. Total energy of universe remains constant

Units and measurement Unit The chosen standard of same time taken time as reference to measure a physical quantity.   Physical quantity Any quantity which can be measured directly or indirectly Characteristics of standard units 1-     It should be well defined 2-     Suitable in size 3-     Easily reproducable at all places 4-     It shouldn’t change from place to place with time 5-     It should be easily accessible

Units and measurement Common System Units CGS System MKS System   CGS System MKS System Length = cm Length = meter Mass = gram Mass = kilogram Time = second Time = second FPS System Length = foot Mass = pound Time = second

SI System Physical Quantity Unit   Length meter Mass kilogram Time second Temperature Kelvin Current ampere Luminous intensity candela Quantity of matter mole Advantage of S.I. 1-Rational system- one unit for one quantity 2-Coherent system- all derived units can be obtain by multiplying and dividing fundamental units It is closely related to CGS System SI is metric system

Measurement of length Smallest unit = nucleus Largest unit = Radius of universe 1025 cm Direct Method By Scale  10-5m - 102m  Indirect Method for long distances  1- Echo method Gun is fired from O time interval between the transmitted and reflected is noted   D = VxT D=VxT

Laser – To find distance of moon Laser – To find distance of moon. Light amplification by stimulated emission radiation.   Thickness of sheet d = (V x T) / 2 Sonar – Sound navigation and ranging d = (C x t) / 2 C= Velocity of waves Radar – Radio Detection and Range. Radio Waves are sending towards aero plane d = (C x t) / 2

To find height if an object triangulation method   Accessible object Sextant -  Tan  = h/X H = Tan  x X  In Accessible Object In  BPA Tan  = h/PA PA = h cot  Tan 2 = h/X +PA H Cot 2 =X + PA QA = H Cot 2 - 2 QA-PA = H Cot 2 - H Cot 1 X= H ( Cot 2 - Cot 1 ) H= h/( Cot 2 - Cot 1)

To Measure size of an astronomical object

Unit of length 1Light year = 9.5 x 1015m 1 Astronomical Unit = 1.5 x 1016m 1Parsec = 3.08 x 1016m

Mass = quantity of a matter contain in a body   Inertial Mass = Mass of the body measure when the body is in translation Motion under the effect of an external force other than gravity Measured by Newton 2 law F= m x a Gravitational mass = Mass of a body measure when body is under the effect of gravity but without motion it is called gravitational motion.

Weight Mass 1- It is a force with earth attracts body W = F = Mg   1-     It is a force with earth attracts body W = F = Mg 2-     It is a vector quantity 3-     Vary from place to place Mass 1-     It is a quantity of matter contain in a body 2-     It is a scalar Quantity Mass is Constant

Planet’s elongation

Dimensional Equations When physical quantity equated to dimensional formula its form Dimensional Equations.   Diff. Types of variable And constant Dimension able variables Ex – area volume velocity etc 2- Non Dimension able variables Ex – angle stain sity etc 3- Dimension Constant Ex- Gravitational Constant, planks constant 4- Non Dimension Constant Ex – Trigonometric Ratio

Significant figure   Digits whose values are accurty Known in a particular Measurement Are its significant figure Rules 1-    All non zero digits are significant 2-    All zeros betw. 2 non zero digits are significant 3-    All zeros to the right of decimal and to left of non zero digit are never significant 4-    All zeros to the right of the decimal are significant if they are not followed by non zero digit 5-    All zero’s to the right of last non zero’s digit after decimal are significant 6-    All zeros to the right of the last non zero digit are not significant 7-    All zeros to the right of the last non digit are not significant