Physics Tips

MEMORIZE THESE :

Translational motion	x = x 0 + v 0 t + 1/2at2	Vƒ = Vo + at
Frictional force	f max = μ Ν	μk < μs always
Uniform circular motion	Fc = mac = mv2 /r	ac= v2 /r
Momentum, Impulse	I = F Δt = ΔM	M = mv
Work, Power	W = F d cosθ	P = ΔW/Δt
Energy (conservation)	ET = Ek + Ep	E = mc2
Spring Force, Work	F = -kx	W = kx2 /2
Continuity (fluids)	A v = const.	ρAv = const.
Current and Resistance	I = Q/t	R = ρl/A
Resistors (series, par.)	Req = R1 + R2 . . .	1/ Req = 1/ R1 +1/ R2
Sound	dB = 10 log 10 (I/I0 )	beats = Δ f
Kirchoff's Laws	Σi = 0 at a junction	ΣΔV = 0 in a loop
Thermodynamics	Q = mc Δ T (MCAT !)	Q = mL
Torque forces	L1 = F1× r1 (CCW + ve)	L2 = F2 × r2 (CW -ve)
Torque force at EQ	ΣFx = 0 and ΣFy = 0	ΣL = 0
Refraction	( sin θ1 )/(sin θ2 ) = v1 /v2 = n2 /n1 = λ1 /λ2	n = c/

USED AS PAIRS :

Memorize as Pairs

F = ma F = qE Similar Form F = KG ( m1 m2 / r2 ) F = k ( q1 q2 / r2 ) V = IR P = IV Paired Use vav = Δ d / Δ t aav = Δ v / Δ t (avg vel, acc) v = λ f E = hf (f = 1/T) Ek = 1/2 mv2 Ep = mgh (kin, pot E) Ρ = F/A Δ Ρ = ρgΔh (pressure Ρ) SG = ρ substance / ρ water ρ = 1 g/cm3 = 103 kg/m3 (Spec Grav) ρ = mass / volume Fb = Vρg = mg (buoyant F) Irms = Imax / √2 Vrms = Vmax / √2 Root Mean Sq 1/ i + 1/ o = 1/ f = 2/r = Power M = magnification = - i/o Optics Note: Specific gravity (SG) is equivalent to the fraction of the height of a buoyant object below the surface of the fluid.

DON’T MEMORIZE,KNOW HOW TO USE :

Ρ + ρgh + 1/2 ρv2 = constant	Bernouilli's Equation	Fluids in Motion
L = L0 (1 + αΔ T )	Linear Expansion	Solids, Temp Δ
A = A0(1 + γΔ T )	Area Expansion
V = V0(1 + βΔ T )	Volume Expansion	β = 3 α
fo = fs (V ± vo )/( V ± vs )	Doppler Effect: when d is decreasing use + vo and - vs
V = Ed for a parallel plate capacitor	d = the distance between the plates
dF = dq v(B sin α) = I dl(B sin α)	Laplace's Law	RH rule
1/ Ceq = 1/ C1 + 1/ C2 + 1/ C3 . . .	Capacitors in Ser. and Par.	Ceq = C1 + C2 . . .
Potential Energy ( PE ) = W = 1/2 QV	Work in Electricity	W = 1/2 CV2
ΔG = ΔH - TΔS	Gibbs Free Energy	ΔG° = -RTln Keq

ATOMIC PHYSICS :

1) alpha (α) particle = 2He4 (helium nucleus); 2) beta (β) particle = -1e0 (an electron); 3) a positron +1e0 (same mass as an electron but opposite charge); 4) gamma (γ) ray = no mass, no charge, just electromagnetic energy; 5) Δ m /Δ t = rate of decay where Δ m = change in mass, Δ t = change in time. 6) If the number of half-lifes n are known we can calculate the percentage of a pure radioactive sample left after undergoing decay since the fraction remaining = (1/2) n . Nelectrons = 2 n2 , where Nelectrons designates the number of electrons in shell n . The state of each electron is determined by the four quantum numbers: principal quantum number n determines the number of shells, possible values are: 1 (K), 2 (L), 3 (M), etc... angular momentum quantum number l, determines the subshell, possible values are: 0 (s), 1 (p), 2 (d), 3 (f), n-1, etc... magnetic momentum quantum number ml , possible values are: ± l , ... , 0 spin quantum number ms ,determines the direction of rotation of the electron, possible values are: ±1/2.

THE BASIC :

sin θ = opp/hyp	cos θ = adj/hyp	tan θ =opp/adj
θ = sin -1 x	arcsec θ = sec-1θ	r2 = x2 + y2

• angle θ may be given in radians (R) where 1 revolution = 2π^R = 360°
• estimate square root 3 as 1.7 and root 2 as 1.4
• cross-sectional area of a tube = area of a circle = πr² where π can be estimated as 3.14 and r is the radius of the circle; circumference = 2πr

SOME UNITS TO MEMORIZE :

• Both work and energy are measured in joules where 1 joule (J) = 1 N × 1 m . {Imperial units: the foot-pound , CGS units: the dyne-centimeter or erg }
• The SI unit for power is the watt (W) which equals one joule per second (J/s) = volts × amperes .
• Current is measured in amperes = coulombs/sec. The units of resistance are ohms, symbolized by Ω (omega), where 1 ohm = 1 volt/ampere.
• The SI unit for pressure is the pascal (1 Pa = 1 N/m² ). Other units are: 1.00 atm = 1.01 × 10⁵ Pa = 1.01 bar = 760 mmHg = 760 torr.
• The SI unit for the magnetic induction vector B is the tesla where 1 T = 1 N/(A)(m) = 10⁴ gauss.

Resultant of Forces

Respiratory Distress Syndrome

Respiratory distress syndrome it is basically disease of infants,they dont have well developed lungs.It can also be cause by insuffiicient surfactant associated proteins that are present on alveolar surface.
Without normal surfactant, the tissue surrounding the air sacs in the lungs (the alveoli) sticks together (because of a force called surface tension) after exhalation, causing the alveoli to collapse. As a result, filling the lungs with air on each breath becomes very difficult, and the delivery of oxygen to the body is impaired.

Conitnous X-rays

The X-ray continues spectrum consists of radiations of all possible wave lengths within a certain range. The characteristic spectra consists of definite wave lengths superimposed on the continuous spectrum. The spectrum lines occur in the form of small groups. To understand difference in their shape you have to go through their origin . ORIGIN:- 1) Sometimes a high velocity electron passes close to the nucleus of an atom within the target of the X-ray tube.During the process the electron experiences a strong Coulomb force of attraction due to the nucleus and is suddenly slowed down, at the same time suffering a deflection in its path. During its retardation the electron emits a pulse of e.m. radiation of energy hf. Since the electron suffers all sorts of collisions the retardation suffered is also different. Hence the energy of the emitted X-rays also vary . Hence the X-ray spectra shows all possible wavelengths within a certain range . This gives rise to a continuous spectra (a continuous curve). 2) In some collisions an electron coming with high velocity penetrate through the outer shells of the electrons and strike against an electron in the inner shell, and knockout an electron from the inner shell of the atom . The incident and the dislodged electrons both escape from the atom causing a vacancy in the innermost K shell. An electron from the outer shell (say L shell) in higher energy state jump to the K shell to fill the vacancy . This gives rise to an X-ray photon of energy hf. This causes a vacancy in the L shell , which is again filled up by another electron jumping from one of the outer shells along with the emission of another X-ray photon of different energy.. This process continues till the outer-most shell is reached, thus resulting in the emission of a series of characteristic X- ray photons. This gives rise to sharp lines or peaks superimposed on the continuous line.

English MCQs

Pronouns:
1-The teacher admits that  a)he is   not  c)wiser than  d)me
2- a)if anyone  b)has any c)doubt, refer   d)he to I
3-The student  a)that won the competition  b)Lived  c)in Paris
4-a)The three representatives,whoever the committee chooses,should be at the meeting tomorrow
b)The three representatives,who the committee chooses,should be at the meeting tommorrow

c)The three representatives,whom the committee chooses,should be at the meeting tommorrow

d)The three representatives,whomever the committee chooses,should be at the meeting tomorrow

5-a)Most workers,whomever was not employed by the auto manufacturer,toiled at one of the millions of the little minnow companies
b-Most workers,who  was not employed by the auto manufacturer,toiled at one of the millions of the little minnow companies
c-Most workers,whoever was not employed by the auto manufacturer,toiled at one of the millions of the little minnow companies
d-Most workers,whom was not employed by the auto manufacturer,toiled at one of the millions of the little minnow companies

6-a)Theres is another factor ,that obviously boosts the reputation of both of these men

b)Theres is another factor  that obviously boosts the reputation of both of these men

c)Theres is another factor which obviously boosts the reputation of both of these men

d)Theres is another factor who obviously boosts the reputation of both of these men

7-a)It is really kind of yours to help me
b-It is really kind of your  to help me
c-It is really kind of you  to help me
d-It is really kind of mine to help me


8-a-Among we men,it was he who always acted as the interpreter
b-Among us men,it was he who always acted as the interpreter
c-Among ourselves  men,it was he who always acted as the interpreter
d-Among ours men,it was he who always acted as the interpreter

9a-we don’t understand why u object to him coming with us.
b-we don’t understand why u object  to his coming with us.

c-we don’t understand why u object to he’s coming with us.

d-we don’t understand why u object to he coming with us.

10a-Din’t U know that it was we who played the joke?
b-Din’t U know that it was us who played the joke?

c-Din’t U know that it was our who played the joke?

d-Din’t U know that it was ourselves who played the joke?

11- a)There is really no reason of you becoming so annoy
- b)There is really no reason of  he becoming so annoy
- c)There is really no reason of yourself becoming so annoy
- d)There is really no reason of your  becoming so annoy

12-ARCHIVES:
a-strings
b-annals
c-boards
d-ships


13-AUPICIOUS:
a-avaricious
b-Propacious
c-Audacious
d-Rapacious


14-ASPERSIONS:
a-condemnation
b-commendation
c- Indignation
d-Vilification

15-BALK:
a-Impede
b-impudent
c-Stalk
d-Adonis

16-BANTAM:
a-Diminutive
b-Nutritive
c-Caulk
d-cover

17-BATTER:
a-Hit
b-Equipoise
c-Dote
d-signal


18-BAMBOOZLE:
a-Demure
b-Delude
c-Decry
d-Defer

19-AUDACIOUS:
a-Meek
b-cheeky
c-Procrastinater
d-Ironic


20-ARBOREAL:
a-sylvan
b-Admantine
c-Abstruse
d-arcane

21-ASCETIC:
a-Ecentric
b-Sage
c-savage
d-Nomadic

22-APPREHENSION:
a-Judgement
b-Detention
c-Brutality
d-Tranquality
23-ATROPHY:
a-Detention
b-degenaration
c-Villification
d-Affinty


24-AVATAR:
a-Prohibition
b-Condemnation
c-Personification
d-meriment


25-BAUBLE:
a-Trinket
b-yoga
c-toss
d-Hurl

An Apology

I apologize for no posting here.I am busy in my engineering universities tests so, as soon as i get free I will update the blog.

NUST Merit 2013