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.