PHYSICS
PHYSICS is Derived from a Greek Word "FUSIS " which means Nature i.e. Physics is Study of nature AND natural phenomenon .
PHYSICS have many branches . Some of these are as follows.
PHYSICS have many branches . Some of these are as follows.
1)Classical Mechanics
2)Wave Mechanics
3)Heat and Thermodyanamics
4)Optics
5)Electricity, Magnetism & Electronics
6)Modern Physics
7)Relativity
8)Solid state physics
9)Nuclear Physics
10)Astrophysics
11)Quantum Mechanics etc.
Up to 12th standard mainly we study above first 6 branches. Normally all boards in India they teach Classical Mechanics,Wave Mechanics & Heat & Thermodyanamics as PAPER 1 and
Optics , Electricity magnetism and Electronics & Modern Physics as PAPER 2 .
Physical quantity : Physical quantities are characteristic or property of an objects which can be measured or calculated by the use of other measurements .
There are three types of physical quantities.
1)Fundamental quantities
2)Derived quantities
3)Suplementary Units
1)Fundamental quantities : Those physical quantities which does not depend on any other physical quantities for their measurements , they can be expressed by themselves are know as fundamental quantities .
Their corresponding units are known as fundamental units.
There are seven fundamental quantities .Their units are known as fundamental units or base units.They are ...
a)Length (l) : It's unit is metre (m) or cm.
b)Mass (m) : It's unit is Kg or gm .
c)Time (t) : It is measured in second (s)
d)Temperature (T) : It is measured in Kelvin(K).
e)Current (I) : It is measured in Ampere (A).
f)Amount of substance : It is measured in mol .
g) Intensity of light (I) :It is measured in Candela (Cd) .
2) Derived Quantities : Those physical quantities which depend on Fundamental quantities for their measurements , are known as derived quantities . Examples of derived quantities are Area , velocity, acceleration , force , density, volume , Pressure , momentum etc.
3) Supplementary Units : There are two supplementary units .
1)Plane angle :It is measured in degree or radian .
2)Solid angle : It is measured in steradian .
We should know some basic defination and units of physical quantities which are used in physics.
1) Motion : It is defined as change in the position of the object with respect to some observer . Means change in the position of the object should be seen by the observer , then only it is motion . If change in the position of the object is not seen by the observer then it is not a motion for that observer.
There are different types of motion . But for simplicity we will catagorise as :-
a)Linear motion or translational motion
b)Angular motion or circular motion
1) Linear Motion ( straight line motion ) or translational motion : Motion of the particle along the straight line .
2) Circular Motion or Angular motion (Rotational motion) : Motion of the particle along the circumference of circle .
3)Uniform circular motion (UCM) : Motion of the particle along the circumference of the circle with uniform speed is called as uniform circular motion.
4)Displacement (S): It is the shortest distance between starting and end point of motion . It is also defined as change in position of the object in a specific direction. it is denoted by S . It is a vector quantitty . It is measured in Meter (m) or centimeter (cm).
5)Distance (S) or(x) : It is a actual path lenght i.e. it is actual distance covered by the body. it is a scalar quantity . It is measured in meter (m) or centimeter (cm).
6)Velocity (V) : It is defined as change in displacement per unit time or it is also defined as time rate of displacement. It is denoted by U or V . It is a vector quantity. It is measured in meter per second(m/s) or centimeter per second (cm/s) .
Velocity = Displacement/time
7)Speed (V) : It is defined as change in distance per unit time or it is time rate of distance . Normally it is denoted by V. It is a scalar quantity . It is measured in meter per second (m/s) or centimeter per second (cm/s) .
Speed= Distance /time
8)Acceleration (a) : It is defined as change in velocity per unit time or it time rate of velocity. It is denoted by 'a '. It is a vector quantity . It is measured in meter per second square (m/s²)or centimeter per second square (cm/s²).
acceleration = Velocity/time or V/t
9)Mass (m) : It is actual matter contained in the body . It is denoted by 'm' . It is scalar quantity. It is measured in kilogram(kg) or gram(g) .
10) Weight (W) : It total gravitational force acting on the body.It is denoted by W. It measured in kilogram meter per second square (Kg m/s²) or gram centimeter per second square (gm cm/s²).
Weight =mg
11)Density (d) : It is the ratio of mass to volume or it is defined as mass per unit volume of an object.
It is measured in kg/m³ or gm/cm³ .
Density =Mass/ volume
12)Force (F) :It is defined as that physical quantity which changes or tries to change the position of the object . It is a vector quantity . It is measured in Newton (N) or Dyne (D) .
1N =10⁵ Dyne .
Force =ma
13)Work (W) :It is a Product of force and displacement . It is Vector quantity. It is one kind of Energy . It is measured in Joule (J) or erg . It is also measured in N m or dyne cm .
1J =10⁷ Erg
Work =F.S
14) Power (P) : It is Capacity to perform work . It Measured in Joule / second (J/s) or Erg per second (Erg/s) .
Power =Work/time =W/t =FS /t=F (S/t )=FV =mav .
15)Energy (E) : It is work. It is meaured in J or Erg .
16)Kinetic Energy (K.E.) : It is energy posses by the body on account of it's motion. It is meaured in J or Erg .
K.E. =1/2mv².
17) Potential Energy (P.E.) : It energy posses by the body on account of it's Configuration or position. It is also measured in J or Erg .
P.E. =mgh
18)Pressure (P) : It is a force acting per unit area . It meaured in Newton per meter square (N/m²) or dyne per centimeter square (Dyne/cm² ).
Pressure =Force/Area =F/A
19)Torque (T) : It is a rotational force which produces circular motion in the body .It is nmeasured in Newton meter (Nm) or dyne cm.
Torque = r F
20 )Couple : It is also a rotational force ,which produces circular motion in the body. It is also defined as two equal and opposite forces acting along same line but in opposite direction. It is also measured in Nm or dyne cm.
Couple =rF
21) Impulse (J) : It is a large force generated for a short interval of time . It is measured in Newton meter (Nm) or dyne cm .
Impulse = F t
22) Momentum (M) : It is a product of mass and velocity . It is measured in Kg m/s or gm cm/s .
Momentum =mv
23 )Angular momentum (L) : It is a product of moment of inertia and angular velocty . It is measured in kg m².rad/sec .
L =Iw
24)Moment of inertia (I) : It is product of mass and square of it's distance from axis of rotation . It is anologous to mass in linear motion . It is measured in Kg m² or gm cm² .
I =MR²
25)Surface tension (T) : It is a force acting per unit length .It is measured in Newton per meter (N/m) or dyne /cm .
Surface Tension = F/l
26)Radius vector (r) : It is a vector drawn from centre to any point on the circumference of the circle .
27)Angular displacement (0) :It is a angle trace by the radius vector at the centre of the circle . It is measured in radian (rad) .
28)Angular velocity (w) : It is a angular displacement per unit time . It is measured in rad/sec.
Angular Velocity = angular displacement/time
29) Angular acceleration (a) : It is a ratio of angular velocity to time . It is measured in rad/sec² .
Angular acceleration =angular velocity /time
30)Time period (T) : It is a time taken by the particle to complete one revolution. It measured in second (sec) .
31) Centripetal force (F) : It is force acting on a particle performing uniform circular motion along the radius towards the centre of the circle .
It is measured in Newton (N) or dyne .
Centripetal force = mv²/r =mrw² =ma
32) Centrifugal force (F) : It is a force acting on the particle performing UCM along the radius but away from centre. It is measured in Newton(N) or Dyne
Centrifugal force = - mv²/r =-mrw² =-ma
33)Stress : Force acting per unit area is knownas stress. It's unit is N/m² i.e. Newton per meter square.
Strees =F/A
34) Strain : It is the ration of change in dimension to original dimension .
It has no unit.
Strain = Change in dimension/original dimension
35)Angle of contact :The angle between the tangents drawn to the free surface of the liquid and surface of the solid at point of contact , measured within the liquid.
36 )Surface Energy : It is amount of energy rquired per unit area to increase the size of the surface of the liquid.
Surface Energy = TA
where T =surface tension , A = area
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