Physics Annotated Formula Sheet Formula Symbol and Units d = displacement in m (meter) Displacement d = x – xo x = position in m + or – depending on direction vav = average velocity in m/s t = change in time in s (second) Constant velocity a = acceleration in m/s2 vav = d/t v = instantaneous velocity in m/s Accelerated motion a = (vt – vo)/t Kinematic formulas d = vot + ½at2 d = ½(vo + vt)t vt = vo + at vt2 = vo2 + 2ad Graphing constant velocity in one dimension d v a Formula Symbol and Units Normal force, Fn, is the force on the object by the surface Ff = force of friction in N Force of friction For static friction: Ff sFn = coefficient of friction For kinetic friction: Ff = kFn Fn = force normal in N Accelerating forces problems. Fn Fp Fp- Ff Fp-|| Fg Fn Fp t t Graphing accelerated motion in one dimension d v a t Vector addition y t t Fg t Bx= BcosB Rx By = BsinB B Ry R A Fg Ff Ay = AsinA Ax = AcosA x Ax + Bx = Rx Ay + By = Ry R = (Rx2 + Ry2)½ tan = Ry/Rx = tan-1(Ry/Rx) add 180o to when Rx is negative Projectile motion (g = gravitational acceleration, -10 m/s2) vertical motion use accelerated motion formulas horizontal motion use constant velocity formula d vo vt a t direction dy vyo vyt -g vertical t dx vx horizontal vc = perimeter velocity in m/s Uniform circular motion r = radius of circle in m vc = 2r/T T = period of motion in s ac = vc2/r ac is directed toward center ac = centripetal acceleration in m/s2 Newton's Laws of Motion 1. Object stay in same motion unless acted upon by a force 2. Acceleration if proportional to force/mass 3. For every action there is an equal, but opposite reaction F = force in N (Newton) Accelerating force F|| = ma m = mass in kg (kilogram) a = acceleration in m/s2 Fs = spring force in N Spring force Fs = kx k = spring constant in N/m x = distance stretched in m Fg = force of gravity in N Force of gravity (weight) Fg = mg m = mass in kg g = 10 m/s2 Fg-|| 1. Label all forces 2. resolve non-||, non- forces into || and components 3. F|| = ma (m is all moving mass) 4. F = 0 m = mass of A and B in kg Masses hanging from a pulley, where mA > mB g = 10 m/s2 (mA – mB)g = (mA + mB)a a = acceleration of system in m/s2 Fc = centripetal force in N Centripetal force m = mass in kg Fc = mac = mv2/r ac = centripetal acceleration in m/s2 v = perimeter velocity in m/s r = radius of circle in m Fg = force of gravity in N Force of gravity between G = 6.67 x 10-11 N•m2/kg2 planets Fg = GMm/r2 M, m = mass in kg r = distance between centers in m Force of gravity is centripetal v = perimeter velocity in m/s GMm/r2 = mv2/r cm = center of mass in m Center of mass cm = m1r1 + m2r2 + ... m = mass in kg (m1 + m2 + ...) r = distance from 0 position in m Non-accelerating force problems where forces act through cm. 1. Draw free body diagram 2. Resolve all forces into x-components and y-components 3. Fx = 0 4. Fy = 0 5. 3 forces, two of which are perpendicular: draw vector sum diagram and solve for missing sides of right triangle Non-accelerating force problems where forces act away from cm. 1. 2. 3. 4. 5. Draw free body diagram Determine axis of rotation that eliminates an unknown F x r = F x r (torque) F = F F = F Formula Work: W = F||d + or – , but no direction Power: P = W/t = Fvav W can be any energy form Kinetic energy: K = ½mv2 Gravitational potential energy near a surface Ug = mgh Gravitational potential energy between planets Ug = -GMm/r Spring potential energy Symbol and Units Formula Symbol and Units W = work in J (Joule) Simple harmonic motion (SHM) T = period in s F|| = force in N m = mass in kg d = distance parallel to F in m k = spring constant in N/m P = power in W (Watt) A = amplitude in m K = kinetic energy in J vo = velocity at midpoint in m/s m = mass in kg v = velocity in m/s Ug = gravity potential energy in J Time to complete one cycle g = 10 m/s2 T = 2(m/k)½ h = height above surface in m 0 ±A displacement G = 6.67 x 10-11 N•m2/kg2 velocity, v vA = 0 vo = 2A/T = A(k/m)½ M = planet mass in kg acceleration, a ao = 0 aA = vo2/A = A(k/m) r = distance center-center in m 2 U = spring potential energy in J potential energy, U U = 0 UA = ½kA2 s o Us = ½kx 2 k = spring constant in N/m kinetic energy, K Ko = ½mvo KA = 0 x = distance stretched in m T = period in s Period of a simple pendulum Energy problems L = length of pendulum in m T = 2(L/g)½ 1. determine initial energy of the object, Eo g = gravity acceleration in m/s2 2. determine energy +/– due to a push or pull: Wp = ±F||d Mechanical wave 3. determine energy removed by friction: Wf = Ffd 4. determine resulting energy, E' = Eo ± Wp – Wf 5. determine d, h, x or v 6. general equation: K + U ± Wp – Wf = K' + U' ½mv2 + mgh + ½kx2 ± Fpd – Ffd = ½mv'2 + mgh' + ½kx'2 p = linear momentum in kg•m/s Linear momentum p = mv m = mass in kg v = velocity in m/s Impulse J = impulse in N•s J = Ft = mv = p amplitude, A: maximum height of a crest or depth of a trough F = force in N measured from the midpoint (m) Kinetic energy to momentum t = time in s K = p2/2m wavelength, : distance between any two successive identical K = kinetic energy in J points of the wave (m) Stationary separation frequency, f: the number of complete waves that pass a given 0 = mAvA' + mBvB' point per unit time (Hz or s-1) Inelastic collision period, T: the time it takes for one wave to pass (s) mAvA + mBvB = (mA + mB)v' conservation of p, but not K T = 1/f Elastic collision velocity, vw: speed of the waveform, vw = /T = f (m/s) mAvA + mBvB = mAvA' + mBvB' transverse wave (string): disturbance wave vA + vA' = vB + vB' longitudinal wave (sound): disturbance wave conservation of p and K Interference Collision in two dimensions amplitudes combine (superposition principle) px: mAvAx + mBvBx = (mA + mB)vx' or mAvAx' + mBvBx' constructive interference when amplitudes are added py: mAvAy + mBvBy = (mA + mB)vy' or mAvAy' + mBvBy' destructive interference when amplitudes are subtracted Ballistic pendulum problems beats, fbeats = |fA – fB| 1. bullet strikes block and sticks vw = velocity of wave in m/s Velocity of a wave on a string mvm + 0 = (m + M)v' Ft = force of tension in N ½ vw = (Ft/) 2. block swings or slides = linear density in kg/m 2 2 swing (K = Ug): ½(m + M)v' = (m + M)gh h = v' /2g Harmonics slide (K = Wf): ½(m + M)v'2 = (m + M)gd d = v'2/2g Moment of Inertia (angular inertia): I = moment of inertia in kg•m2 I = mr2 m = mass in kg r = radius of circular path in m point mass in a circular orbit L = angular momentum in Angular momentum kg•m2/s L = I = rp = rmv = angular velocity in rad/s point mass in a circular orbit p = linear momentum in kg•m/s Conservation of angular v = linear velocity in m/s momentum: r1v1 = r2v2 Determining nth harmonic = wavelength in m E = energy in J Matter energy equivalence L = length of string in m n = 2L/n E = mc2 m = mass in kg n = number of harmonic fn = nf1 c = 3 x 108 m/s f = frequency Binding energy, BE mnuclide + mBE = mp + mn f' = perceived frequency in s-1 Doppler effect f’ = f(v ± v )/(v ± v ) f = generated frequency in s-1 w o w s Nuclear reactions approaching: f' > f (+vo, –vs) vw = wave velocity in m/s proton: 11p, neutron 10n, electron 0-1e, positron 01e receding: f' < f (–vo, +vs) vo = observer velocity in m/s alpha: = 42He, beta: = 0-1e vs = source velocity in m/s approximation formula conservation of mass # & charge: 23892U 42He + 23490Th 2 f/f v/v w nuclear process: mproducts – mreactants = mBE < 0 (E = mc ) approaching: f’ = f + f half life: 1 ½ ¼ take same amount of time t½ receding: f’ = f – f Formula Symbol and Units Angle of reflection i = incoming ray to surface i = r r = reflected ray to surface phase shift when ni < nr n = index of refraction c = 3 x 108 m/s Wave velocity in a vacuum f = frequency of wave in s-1 (Hz) c = f = wavelength in m Refraction within a medium n = index of refraction (no units) vn = c/n vn = velocity at n in m/s fn = f1 n = 1/n Angle of refraction (Snell's law) ni = source medium n nisini = nRsinR i = incident angle to surface ni < nR: bend toward normal nR = refracting medium n ni > nR: bend away from normal R = refracted angle to surface n to f color separation = dispersion (prism) total reflection when ni > nR and i c = nlow/nhigh r = radius of curvature in m Parabolic mirror radius of curvature r = 2f f = focal length in m do = object distance to l/m in m lens/mirror equation di = image distance to l/m in m 1/do + 1/di = 1/±f f = focal length in m +di for real image (-di virtual) +f for converging (-f diverging) M = magnification (no units) hi = height of image in m magnification equation ho = height of object in m M = hi/ho = -di/do do > +f do < +f –f Formula Density = m/V Symbol and Units = density in kg/m3 m = mass in kg V = volume in m3 kg/m3 = g/cm3 x 103 s.g. = specific gravity (no units) Specific gravity s.g. = mair/(mair – mfluid) mair = mass measured in air mfluid = submerged mass object = s.g. x fluid P = pressure in Pa (Pascals) Pressure on a surface P = F/A F = force in N A = Area in m2 Force on a hydraulic piston PPa = Patm x 105 Fin/Ain = Fout/Aout P = pressure in Pa Pressure in fluid at a depth f = density of fluid in kg/m3 P = fgh g = 10 m/s2 h = depth in m Upward force on a submerged Fb = buoyant force in N object (Archimedes principle) f = density of fluid in kg/m3 g = 10 m/s2 Fb = fgVo Vo = object's submerged volume V/t = volume flow rate in m3/s Fluid flow in a pipe A = area at a position in m2 V/t = Av = Constant v = velocity at a position in m/s Solve plumbing, lift & tank leak P = pressure on fluid in Pa problems (Bernoulli's equation) = density of fluid in kg/m3 g = 10 m/s2 P + gy + ½v2 = Constant y = elevation in m v = velocity in m/s Thermal expansion L = change in length in m = expansion coefficient in o C-1 L = LoT Lo = original length in m T = temperature change in o C K = kinetic energy in J Kinetic energy of gases R = 8.31 J/mol•K 3 K = /2RT Interference with two slits = angle from slits to band in m T = Temperature in K tan = x/L x = center to band distance in m Velocity of gas molecules v = velocity in m/s L = slits to screen distance in m M = molar mass in kg sinc = m/d ½ v = (3RT/M) m = band order (no units) P = pressure in Pa sind = (m + ½)/d V = volume in m3 Ideal gas law c for bright band (d for dark) = wavelength of light in m n = number of moles d = distance between slits in m PV = nRT Interference with one slit TK = ToC + 273 W = width of light spot W = 2L/d' d' = width of slit PV diagram +Win (-Wout) toward y-axis, -Win (+Wout) away from y-axis Thickness of a film, T (f = 1/n) +T and +U away from origin (P x V) ni < nf < n r nf > ni and nr Interference PV (heat engine) problems Bright U = internal energy change in J T = ½f T = ¼f U = 3/2nRT = 3/2PV = 3/2PV n = number of moles Dark T = ¼f T = ½f R = 8.31 J/mol•K Win = -PV = Area EM Radiation Qin = heat added to system in J U = Qin + Win High energy has short , high f (low energy has long , low f) For complete cycle: U = 0 Win = work on the system in J Transverse wave polarizable Process T U = Qin + Win Doppler shift: moving away = shift to longer (red shift) 3/ PV 0 Isometric(V = 0) PV/nR U E = Energy in J Photon energy 2 3/ PV E = hf = mc2 h = 6.63 x 10-34 J•s Isobaric(P = 0) PV/nR U – Win -PV 2 UV > violet ... red > infrared f = frequency in s-1 0 0 -Win -Qin Isothermic (T = 0) Photon momentum m = relativistic mass in kg Adiabatic (Q = 0) W 0 ? U in p = mc = h/ = E/c c = 3 x 108 m/s ec = ideal efficiency (no units) Efficiency of a heat engine Particle wavelength (De Broglie) = wavelength in m ec = (Thigh – Tlow)/Thigh T = temperature in K p = momentum in kg•m/s particle = h/p e = |Wcycle|/Qin e = actual efficiency (no units) Atomic energy levels (Bohr model) En = electron energy in eV Q/t = rate of heat flow in J/s Rate of heat flow through a En = -B/n2 B = 13.6 eV for hydrogen A = area of barrier in m2 barrier n = energy level (1, 2, etc.) Energy absorbed by an atom TH = high temperature in o C Q/t A(TH – TL)/L EeV = photon energy in eV EeV = En-high – En-low TL = low temperature in o C nm = wavelength in nm EeV = 1240 eV•nm/nm L = thickness of barrier Kelectron = kinetic energy in eV Heat gain/loss by a material Photoelectric effect Q = heat in J Kelectron = Ephoton - Ephoton = 1240 eV•nm/nm m = mass in kg Q = mcT Kinetic energy of an electron = work function in eV c = specific heat in J/kg•K me = 9.11 x 10-31 kg 2 Kelectron = ½mev v = electron velocity in m/s Formula Symbol and Units Conducting sphere: excess charge on outer surface, E = 0 inside Electric force between charges Fe = electric force in N Fe = k|Qq|/r2 k = 9 x 109 N•m2/C2 attract for unlike (repel for like) Q, q = charge in C (Coulombs) r = Q1 to Q2 distance in m Electric field around a charge E = electric field in N/C or V/m E = k|Q|/r2 away from +Q (toward -Q) Electric field around multiple charges Calculate E for each charge Combine E (add for same direction, subtract for opposite direction, use Pythagorean and tan = y/x for fields) E = 0 between like charges and closer to lesser |Q| E = 0 outside unlike charges and closer to lesser |Q| Force on q in electric field E Fe = electric force in N Fe = |q|E q = charge in C +q: E , Fe –q: E , Fe E = electric field in N/C Ue = electric potential energy in J Electric potential energy between charges Ue = kQq/r k = 9 x 109 N•m2/C2 +Ue for like (-Ue for unlike) Q, q = charge in C (Coulombs) r = Q1 to Q2 distance in m Electric potential (voltage) V = potential (voltage) in V (volts) around a charge V = kQ/r +V for +Q (-V for –Q) Electric potential around multiple charges Calculate V for each charge Combine V (add +V and subtract -V) V = 0 between unlike charges and closer to lesser |Q| V = 0 infinitely far away from like charges Ue = electric potential energy in J Electric potential energy on a q = charge in C charge in an electric potential Ue = qV V = voltage (potential) in V Kinetic energy equals loss in Ue m = mass in kg v = velocity in m/s K = -Ue ½mv2 = |qV| Current flow I = current in A (amperes) I = Q/t Q = charge in C t = time in s Resistance in wires R = resistance in (ohms) = resistivity in •m R = L/A L = length in m A = cross-section area in m2 V = terminal voltage in V Battery terminal voltage E = emf in V V = E ± IR I = current in A + when battery is recharging – when battery is discharging R = internal resistance in V = voltage in V Voltage loss (Ohm's law) V = IR I = current in A Power consumed R = resistance in P = power in watts W P = IV = V2/R = I2R C = capacitance in F (farads) Capacitor capacitance C = єoA/d єo = 8.85 x 10-12 C2/N•m2 A = plate area in m2 Capacitor store charge d = plate separation in m Q = CV Q = charge in C Capacitor store energy V = voltage in V 2 2 UC = ½QV = ½CV = ½Q /C U = stored energy in joules J C Electric field between capacitor E = electric field in V/m plates E = V/d V = voltage in V d = distance between plates Direction is from Vhigh Vlow Variable Capacitor problems Adjust A or d Capacitance Battery Connection Connected Disconnected C = єoA Area Distance (A) (d) d Q = C x V Q = C x V Formula Circuit Element Symbols Symbol and Units Battery Capacitor Resistor Summary Chart for Circuit Elements in Series and Parallel Element S/P Formula Constant Variable Rs = R1 + R2 Series Is Vn = IsRn Resistor 1/Rp = 1/R1 + 1/R2 Vp Parallel In = Vp/Rn 1/Cs = 1/C1 + 1/C2 Qs Vn = Qs/Cn Series Capacitor CP = C1 + C2 Vp Qn = CnVp Parallel Kirchhoff’s Circuit Rules loop rule: V = 0 for any complete circuit junction rule: Iin = Iout for any junction General steps for solving a circuit problem 1. Determine overall resistance: combine Rp until all Rs 2. Determine the overall current of the circuit: I = Vtot/Rtot 3. Determine voltage loss in series resistors: V = ItotR 4. Determine voltage in parallel components: Vp = Vtot – Vs 5. Determine I and P for each resistor: I = V/R, P = IV 6. Determine Q and UC for each capacitor: Q = CV, Uc = ½QV Measuring I and V I: place ammeter between battery and circuit element (series) V: attach voltmeter to each side of circuit element (parallel) FB = force in N Magnetic force on a moving charge: FB = qvB q = charge in C v = velocity in m/s Magnetic forces are centripetal B = magnetic field in T qvB = mv2/r palm toward center of circle path m = mass in kg r = radius of circular path in m Magnetic force on current wire I = current in A FB = ILB L = length of wire in m Direction F B I, v Magnetic field near a wire I out I in B B = k'I/r B Magnetic field in a solenoid B out B in B = magnetic field in T (teslas) k' = 2 x 10-7 T•m/A I = current in A r = distance from wire m o = 4 x 10-7 T•m/A N = number of turns L = length in m I B = oI(N/L) I Magnetic force between wires FB = k'I1I2L/r Direction: I1 I2 = attraction Permanent Magnetics Magnetic field lines go from north pole to south pole Earth's north magnetic pole is at the south geographic pole Magnetic flux B = flux in Wb (weber) A = enclosed area to B in m2 B = A x B B = magnetic field in T Induced emf in a wire loop E = emf in V B = change in flux in Wb E = B/t t = time in s Induced emf in a moving rod v = velocity of rod in m/s L = distance between rails m E = vLB B = magnetic field in T Direction of induced current B Induced Current thumb (increase: flip, decrease: no flip) I = E/R increase clockwise (rotate || to , move B closer) Up decrease counter clockwise increase counter clockwise Down decrease clockwise