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Class 12 CBSE Notes 2017 : Physics

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Nishant kumar Singh
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Data Scientific Method 3. Uncertainty 1. Observation * units (metrics) 2. Define the Problem * measuring 3. Test/Experiment * sig. figs. 4. Hypothesis * Data 5. Collect Data/Manipulate Manipulation 6. Conclusion Accuracy vs. Precision Accuracy closeness of results to a standard Precision closeness of results to each other *use same piece of equipment to collect data* Qualitative vs. Quantitative Qualitative more on precision than accuracy Quantitative numbers count and are important Sig. Figs. Addition and Subtraction: *least # places after decimal Multiplication: *places after decimal count as sig. figs. 2 . 5 cm = 1 in Vectors Vectors (velocity) has BOTH magnitude and direction Scalars (speed) has magnitude ONLY *time, mass, volume Metric System Abbr. Mm - km - hm - dkm - m dm - cm - mm - Mm(E-6) - nm(E-9) ------------------------------------------------------------------------------------------------------- Mult. Component Vecctors 1. 18m due S 2. 22m, 47deg. S of W 3. 10 m, 78deg. N of W 4. 30 m due E *(W&E) Sum of the V = (0)+ (-22 cos47)+(-10 cos78)+(30) =12. 9m *(N&S) Sum of the V = (-18)+ (-22 sin47)+(10 sin78)+(0) =-24. 3m *Resultant = ((12. 9)2 + (24. 3)2)1/2 =27. 5m * = tan-1(24. 3) (12.9) = 62.0deg R= 28m, 62deg S of E ------------------------------------------------------------------------------------------------------- Kinematics Displacement If + it s AWAY If it s TOWARD Velocity (m/s) Use ONLY when SPEED is CONSTANT 1. does not include acceleration 2. does not include starting and stopping in the same place v= t Acceleration (m/s/s) *speeding up or slowing down a= v t Kinematic Formulas X Direction Y Direction = o+at -gt 2 = o + Vo t + a t - gt2 = o + ( + o) t ----- 2 = o 2 + 2 a ( - o) -2g( Change (o) to Y(o) Projectial Motion Half * Y determines time in air *compliment angles of 45deg have same range X . . Y . =V t Y= gt2 T= V Full * 45deg has max. range Steps: 1. o cos o / o sin o Find the TIME (check Y) Find the height / range X . Y . =V t t= 2 o . (Vx = o cos o) g (V o = o sin o) y max = o 2 2g --------------------------------------------------------------------2. 3. Force (N) - Causes a change in motion (causes acceleration) - Is a VECTOR quantity Equilibrium no acceleration , forces cancel , at rest Newton s Laws of Motion 1. An object at rest will remain at rest until acted upon by an outside force INERTIA directly related to mass 2. Acceleration is directly related to Force indirectly related to mass F=ma (1 kg m / s2 = 1 Newton) Action = equal and opposite reaction -can t have only one force F a, b = - F b, a Normal Force - able to change until breaking point of whatever it s holding - acts perpendicularly to holding object - comes from ground (except water) Newtons 1 N = 0. 225 lbs. Mass is constant F= ma ------ Fw = mg N kg (/ 9. 8) Kg N (x 9. 8) Friction (Ff) 1. two or more things must be touching 2. energy is transferred (heat, sound, etc) 3. texture matters NOT SURFACE AREA = coefficent of friction (Ratio of parallel force to perp. Force) = Ff (3 decimal places) FN Ff = m g Ff = Fw (on flat surface) = tan (when is constant) Pressure: P = Force/area 4. opposes motion which causes decelleration 5. static starting Ff not moving (rolling) greater force than kinetic kinetic moving (rolling, sliding, fluid) Equilibrium Translational: the sum of forces equal zero Rotational: the sum of torques equals zero Complete: must have BOTH Center of Gravity : center of distribution of mass Torque Force with leverage causes rotation Leverage: distance from fulcrum to force *Directly related to torque = F (perp.) l Impulse A change in momentum (how you feel p change) Force : F = m a F = m v t Time : * hidden variable* F t = m = p Conservation of Momentum In the absence of an external force, the total momentum of a system is constant m1 1 + m2 2 = m1 1 + m2 2 Work ( J ) * Need to apply force W=Fd * implies motion Power ( watt -- w ) P = W . = (F d) t t J = 1 w = N m = 1 kg m2 2 s s s 1 horse power = 746 w Energy Ability to do work Mechanical: energy of motion or position Kinetic (K) : motion K = m 2 (J) Potential (U) : position U = m g h (J) (W = F d) When not given distance (or force) W = m 2 - m o2 (W = K) (K final) (K initial) Conservation of Energy Energy change from one to the other w/o any net loss UTOP = KBOT (mgh = 1/2mv2) Wave Motion Simple Harmonic Motion A repeating motion in which the acceleration is directly related to the displacement (distance away from the equilibrium) and always directed towards equilibrium. ------------------------------------------------------------------------------------------------------- Circular Motion Moving at a constant speed while accelerating A = v speed: constant dxn: constantly changing Centripetal Acceleration Inward seeking Ac = 2 . r Centripetal Force Causes centripetal acceleration Fc = m Ac (F = m a) Fc = m 2 . (N) r You MUST have cent. F to keep something moving in a circle Centrifugal: body s interpretation of cent. F DOES NOT EXIST feels inertia Rotation: spinning on axis within object Revolution: spinning on axis outside of object Linear / Angular Linear : speed = distance / time radius matters 57. 3deg = 1 RADIAN 1 rotation = 2 Radians = 360 degrees Angular: speed = # rotations or revolutions / time radius does NOT matter * by doubling the angular speed you double the # of rotations Linear Angular (m) =r (RAD) (m/s) = r (RAD / s) a (m/s/s) a = r (RAD / s / s) F (N) Ft = (Nm) Mass (m) I (mr) F=ma =I For linear = o+ t See other corner = o + o t + t 2 = o + ( + o) t 2 = o 2 + 2 ( - o) Rotational Inertia Resistance to begin or stop rotation Depends on amount of mass AND where it is placed Solid Sphere 2/5 mr2 Solid Disk mr2 Hollow Sphere 2/3 mr 2 Hollow Disk 1 mr2 Velocity is indirectly related to Inertia Shape of object spinning makes the difference while spinning 3 Forces acting upon an object in circular motion 1. 2. 3. Centripetal Acceleration (Ac) Angular Acceleration ( ) Linear Acceleration ( a ) ------------------------------------------------------------------------------------------------------- Conservation Laws Momentum ( N s ) Moving inertia (Newton s 2nd law) Momentum IS inertia Inertia is NOT momentum Momentum is DIRECTLY related to mass and speed p = m (N s) causes body to want to fly off tangent f = 1/T Cosine Curves Y = A cosB (x C) + D A = amplitude ( 0) : how much energy it has CosB = period ( 2 PIE / t) : time, 1 oscillation C = horz. Shift : human error D = vert. Shift : distance, to x-axis Waves * Graphed SHM, transfer of energy Vibration : WORK to get energy Propagates : what energy moves through Mechanical (light) Electromagnetic (sound) Needs a medium does NOT need a medium More dense better less dense better Mechanical Waves Transverse : medium vibrates perp. to energy Most common ex. Guitar string, slinky Longitudinal : medium vibrates para. to energy Has compressions ex: sound Surface : both para. and perp. to energy physics bob ex: earthquakes, waves Principle of Superposition Constructive Interference : added Deconstructive : subtracting (adding negatives) V= _ V = f T Standing Wave A continuous wave train of equal amplitude (RAD), wavelength (m), and frequ. (Hz) (/sec) in the same medium creating nodes and antinodes. Boundary : change in medium (part of energy gets reflected, part gets absorbed) rigidity : how much energy gets ABSORBED close rigidity more absorbed different rigidity more reflected Interference in Diffraction Crest + crest = antinode Crest + troph = node ------------------------------------------------------------------------------------------------------- Sound A range of longitudinal wave frequ. to which the human ear is sensitive Infra sonic sonic spectrum ultra sonic (below 20 Hz. ) (20 Hz 20,000 Hz) (20,000 Hz +) 1. 2. 3. production : needs vibration transition : needs a medium air reception : must be heard V sound = 340 m/s V sound = 331 + . 6 (Temp.) Intensity : measurable How loud a sound is * the time of flow of energy per unit area I = Pow . ( P=W) Amp t Intensity is DIRECTLY related to amplitude Damping : further you get from the center quieter it will be Inverse Square Law : I1 r12 = I2 r22 Volume (B): subjective (decibels) Relative Intensity Level loudness level Volume is DIRECTLY related to Intensity Volume is DIRECTLY related to Frequency f standard = 1,000 Hz. Intensity Range Threshold of hearing (Io) = 1 x 10 -12 w / m 2 Threshold of sound = 1 w / m 2 = 10 log ( I ) 1 x 10 -12 w / m 2 How many powers of 10 are in that number? Decibel = w / m 2 . w / m2 Pitch and Tone I volume f pitch Notes and tones : pitch with recognizable frequencies Laws of Pitch: 1. 2. 3. 4. f is INDIRECTLY related to length f is DIRECTLY related to tension (Ft) f is INDIRECTLY related to diameter (d) f is INDIRECTLY related to density (D) Beats : the resultant interference pattern of 2 notes close in frequency but not exact Creat nodes (sharps and flats) Doppler Effect : the apparent change in frequency of a sound due to the relative motion of either the observer or the source of both Resonate : when you cause something to vibrate at its natural frequency Music repeating wave pattern Noise no repeating wave pattern Consonance sounds GOOD Dissonance sounds BAD Decibel: I B . 1 x 10 12 0 db 11 1 x 10 10 db 1 x 10 10 20 db ---- 2 1 x 10 100 db 1 x 10 1 110 db 1 120 db Natural Frequencies l = 170 / Hz Brass/String n name synm wavl ( ) l f f fund. 1st har. 2l v/2l f 2 1st ov. 2nd har. l v/l f 3 2nd ov. 3rd har. 2/3l 3/2 3v/2l f 4 3rd ov. 4th har. 1/2l 2 2v/ l fn= n hn = 2 l fn = Nf1 2l n Woodwind n name synm wavl ( ) l f f fund. 1st har. 4l 1/4 v/4l f 2 -------------------- ---f 3 1st ov. 2rd har. 4/3l 3/4 3v/4l f 4 -------------------- ---f 5 2nd ov. 3rd har. 4/5l 5/4 5v/4l fn=n hn = 4 l 4l n Instruments String Produced by: plucking string, bowing Change pitch : length, diameter, tension, density Brass Produce by : buzzing mouth piece Change pitch : length of pipe (valves), buzzing Woodwind Produced by : reed vibrating Change pitch : pads, holes Edge tones: narrow streams of air split by edge Helmholtz Resonance: edge tone with bottle (open hole) --------------------------------------------------------------------Light Particle Wave + Newton said so + Thomas Young 2 slit ex + Beams / Waves + reflection, refraction, + travel in straight lines diffraction, interference +Hertz light is energy + Einstein wave particle duality Polarized Light: Light oriented to one plane (calc.) Liquid Filter Display : lets only one degree of light in Visible Spectrum : Radio * Micro * Infrared * Ultraviolet * Xrays* Gamma Big wavelength Small wavelength Red Orange Yellow Green Blue Indigo Violet Transparent: see through it and light passes (Windows, glass) Translucent: can NOT see through it, light passes (frosted glass) Opaque : can NOT see through it, NO light passes Source: makes and emits light Luminous: sun Luminate: moon Light Year: takes 8. 3 min. to get light from sun Dispersion: breaking up light into colors (prism) Colors Cones in eye pick up 3 primary colors of light Additive Primary Secondary BLUE YELLOW RED CYAN GREEN MAGENTA * More than one light source

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