20 17 Weather stations monitor the position of storm clouds. (a) A microwave pulse is emitted from a transducer at a weather station. The pulse reflects from a storm cloud and is detected at the same transducer 340 µs later. Calculate the distance between the storm cloud and the weather station. (3) ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... Distance = ....................................................... 21 Turn over (b) The movement of a storm cloud is monitored by two weather stations. The components of the velocity of the storm cloud towards each weather station are shown in the diagram. N Weather station 1 Weather station 2 9 m s−1 12 m s−1 Not to scale Determine the velocity of the storm cloud. (4) ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... Magnitude of velocity = ....................................................... Direction of velocity = ....................................................... 22 (c) (i) A raindrop is falling vertically through the air. The free-body force diagram shows the forces acting on the raindrop. Diagram NOT drawn to scale viscous drag upthrust weight The raindrop is travelling at terminal velocity. The raindrop is spherical with a radius of 0.10 mm and a weight of 4.1 × 10−8 N . Calculate the magnitude of the terminal velocity. viscosity of air = 1.3 × 10−5 Pa s density of air = 1.2 kg m−3 (4) ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... Magnitude of terminal velocity = ....................................................... 23 (ii) The value of terminal velocity calculated using the data in (c)(i) is greater than the actual terminal velocity of the raindrop. Explain why the calculation in (c)(i) may not be valid. (2) .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. (Total for Question 17 = 13 marks) TOTAL FOR SECTION B = 24 MARKS TOTAL FOR PAPER = 80 MARKS 24 List of data, formulae and relationships Acceleration of free fall g = 9.81 m s–2 (close to Earth’s surface) Electron charge e = –1.60 × 10–19C Electron mass me = 9.11 × 10–31kg Electronvolt 1 eV = 1.60 × 10–19J Gravitational field strength g = 9.81 N kg–1 (close to Earth’s surface) Planck constant h = 6.63 × 10–34J s Speed of light in a vacuum c = 3.00 × 108m s–1 Mechanics Electricity Potential difference V W Q = Resistance R V I = Electrical power and energy P = VI P = I 2R P V R = 2 W = VIt Resistivity ρl R A = Current I Q t = ∆ ∆ I = nqvA Kinematic equations of motion s u v t = + ( ) 2 v = u + at s = ut + 1 2 at2 v2 = u2 + 2as Forces ΣF = ma g F m = W = mg moment of force = Fx Momentum p = mv Work, energy and power ΔW = FΔs Ek = 1 2 mv2 ΔEgrav = mgΔh P E t = P W t = efficiency = useful energy output total energy input efficiency = useful power output total power input 25 Materials Waves and Particle Nature of Light Wave speed v = fλ Speed of a transverse wave on a string T v μ = Intensity of radiation I P A = Power of a lens P f = 1 P = P1 + P2 + P3 + … Thin lens equation 1 u + = 1 1 v f Magnification for a lens m v u = = image height object height Diffraction grating nλ = d sin θ Refractive index n1 sin θ1 = n2 sin θ2 n c v = Critical angle sin C n = 1 Photon model E = hf Einstein’s photoelectric equation hf = ϕ + ½mv 2 max de Broglie wavelength λ = h p Density m ρ V = Stokes’ law F = 6πηrv Hooke’s law ΔF = kΔx Young modulus Stress F σ A = Δ Strain x ε x = σ E ε = Elastic strain energy ΔEel = 1 2 FΔx 26 BLANK PAGE 27 BLANK PAGE 28 BLANK PAGE