Physics (AS & A Level) Paper 21

(density =) mass / volume [1]

d = [(6 × 7.5) / (π × 8100)]1/3 = 0.12(1) m [1]

percentage uncertainty = (4 + 5) / 3 (= 3%) or fractional uncertainty = (0.04 + 0.05) / 3 (= 0.03) absolute uncertainty (= 0.03 × 0.121) = 0.0036 d = 0.121 ± 0.004 m [3]

force per unit positive charge [1]

time = 5.9 × 10–2 / 3.7 × 107 = 1.6 × 10–9 s (1.59 × 10–9 s) [1]

E = V / d = 2500 / 4.0 × 10–2 = 6.3 × 104 N C–1 (6.25 × 104 or 62500 N C–1) [2]

a = Eq / m or F = ma and F = Eq = (6.3 × 104 × 1.60 × 10–19) / 9.11 × 10–31 = 1.1 × 1016 m s–2 [2]

s = ut + ½at 2 = ½ × 1.1 × 1016 × (1.6 × 10–9) 2 = 1.4 × 10–2 (m) distance from plate = 2.0 – 1.4 = 0.6 cm (allow 1 or more s.f.) [3]

electric force ≫ gravitational force (on electron)/weight or acceleration due to electric field ≫ acceleration due to gravitational field [1]

vX–t graph: horizontal line at a non-zero value of vX vY–t graph: straight line through the origin with positive gradient [2]

force/load is proportional to extension/compression (provided proportionality limit is not exceeded) [1]

k = F / x or k = gradient k = 600 N m–1 [2]

(W =) ½kx2 or (W =) ½Fx or (W =) area under graph (W =) 0.5 × 600 × (0.040) 2 = 0.48 J or (W =) 0.5 × 24 × 0.040 = 0.48 J [2]

1. (EK =) ½mv2 = ½ × 0.025 × 6.02 = 0.45 J [2]

2. (work done against resistive force =) 0.48 – 0.45 [= 0.03(0) J] average resistive force = 0.030 / 0.040 = 0.75 N [3]

efficiency = [useful energy out / total energy in] (×100) = [0.45 / 0.48] (×100) = 0.94 or 94% [2]

the number of oscillations per unit time of the source/of a point on the wave/of a particle (in the medium) [2]

or the number of wavelengths/wavefronts per unit time (M1) passing a (fixed) point (A1)

T or period = 2.5 × 250 (µs) (= 625 µs) frequency = 1 / (6.25 × 10–4) or 1 / (2.5 × 250 × 10–6) = 1600 Hz [2]

for maximum frequency: fo = fsv / (v – vs) 1640 = (1600 × 330) / (330 – vs) vs = 8(.0) m s–1 (8.049 m s–1) [2]

loudspeaker moving towards observer causes rise in/higher frequency loudspeaker moving away from observer causes fall in/lower frequency [2]

or repeated rise and fall/higher and then lower frequency (M1) caused by loudspeaker moving towards and away from observer (A1)

wave incident on/passes by or through an aperture/edge wave spreads (into geometrical shadow) [2]

nλ = d sinθ substitution of θ = 90° or sinθ = 1 4 × 500 × 10–9 = d × sin 90° line spacing = 2.0 × 10–6 m [3]

wavelength of red light is longer (than 500 nm) (each order/fourth order is now at a greater angle so) the fifth-order maximum cannot be formed/not formed [2]

charge forms) other to electrical (from ed) (transform energy or done work [1]

1. V = IR or E = IR I = 14 / 6.0 = 2.3 (2.33) A [2]

2. total resistance of parallel resistors = 8.0 Ω current = 14 / (6.0 + 8.0) = 1.0 A [2]

P = EI (allow P = VI) or P = V2 / R or P = I2R change in power = (14 × 2.33) – (14 × 1.0) or (142 / 6.0) – (142 / 14) or (2.332 × 6.0) – (1.02 × 14) = 19 W (18 W if 2.3 A used) [2]

I = Anvq ratio = (0.50n / n) × (1.8 A / A) or ratio = 0.50 × 1.8 = 0.90 [2]

hadron not a fundamental particle/lepton is fundamental particle or hadron made of quarks/lepton not made of quarks or strong force/interaction acts on hadrons/does not act on leptons [1]

proton: up, up, down / uud neutron: up, down, down / udd [2]

composition: 2 (uud) + 2 (udd) = 6 up, 6 down / 6u, 6d [1]

most of the atom is empty space or the nucleus (volume) is (very) small compared to the atom [1]

nucleus is (positively) charged the mass is concentrated in (very small) nucleus/small region/small volume/small core or the majority of mass in (very small) nucleus/small region/small volume/small core [2]