Formula Sheet for Stage 6 Physics

How to Use the Formulas for Stage 6 PhysicsPreliminary CourseFormula Name Comments Typical Problem Typical Answerv = fλWave v= velocity (m/s)Calculate the wavelengthv 3Equation f = frequency (hz)of a water wave travellingv = f λ ∴λ= = = 0. 5mf 68.2.1 λ = wavelength (m)at 3 m/s whose frequency⎛ ⎜⎝I ∝ 1 2d2⎞⎟⎠v 1 sin i= ( =1nsin rv2)Intensity Law8.2.3Snell’s Law8.2.4rr FElectric FieldE =q8.3.2R = V IEnergy = VItP=VIOhm’s Law8.3.2ElectricalEnergy8.3.4ElectricalPower8.3.4I = intensity (no units)d = distance (m)v 1 = speed in first mediumv 2 = speed in second mediumsin i = angle in first mediumsin r = angle in second medium• Angles are alwaysmeasured to the normalE = Electric field (N/C, V/m)F = Force (N)q = charge (C)R = resistance (Ω)V = voltage (V)I = current (A)Energy (J)V = voltage (V)I = current (A)T = time (s)P = power (W)V = voltage (V)I = current (A)is 6 Hz.A globe is viewed from 2metres at a certainbrightness. How brightdoes it appear 6 metresaway?A light ray travelling at 3X 10 8 m/s in air enters apool of water at 45° to thenormal. If it slows downto 2.4 X 10 8 m/s, what isits angle in the water?What is the force exertedon a 2 X 10 -6 C chargemoving in an electric fieldof size 5 X 10 3 V/m?What is the currentthrough a 6Ω resistorwhen a voltage of 18 V isapplied across it?How much energy isdelivered to an electrickettle if a current of 2A isused for 3 minutesplugged into the mains(240V)?What current is requiredby a 2400W electric heaterplugged into the mains(240V)?⎛ 1 ⎞⎜1I ∝ ⎟∴d→ 3d,→⎜2⎟2⎝ d ⎠dbright.v = ∴sinrsin r=v1 sin i v2sin2v1i19thus it appears 9 times less8 o2.4 × 10 sin 45 o== 3883×10rr F−63E = ∴F= qE = 2 × 10 X 5 × 10 = 0. 01NqV V 18R = ∴ I = = = 3AI R 6Energy = VIt = 240 X 2 X 3 X 60 (sec)= 86400 = 86.4 kJP 2400P = VI ∴ I = = = 10AV 240