9702_w16_qp_41
A paper of Physics, 9702
Questions:
12
Year:
2016
Paper:
4
Variant:
1
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1
A satellite is in a circular orbit of radius r about the Earth of mass M, as illustrated in . Earth mass M satellite r The mass of the Earth may be assumed to be concentrated at its centre. Show that the period T of the orbit of the satellite is given by the expression T 2 = 4π2r 3 GM where G is the gravitational constant. Explain your working. A satellite in geostationary orbit appears to remain above the same point on the Earth and has a period of 24 hours. State two other features of a geostationary orbit. 1. 2. The mass M of the Earth is 6.0 × 1024 kg. Use the expression in to determine the radius of a geostationary orbit. radius = m A global positioning system (GPS) satellite orbits the Earth at a height of 2.0 × 104 km above the Earth’s surface. The radius of the Earth is 6.4 × 103 km. Use your answer in and the expression T 2 ∝ r3 to calculate, in hours, the period of the orbit of this satellite. period = hours
13. Gravitational fields  →  13.2. Gravitational force between point masses
13. Gravitational fields  →  13.3. Gravitational field of a point mass
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2
An ideal gas initially has pressure 1.0 × 105 Pa, volume 4.0 × 10−4 m3 and temperature 300 K, as illustrated in . 1.0 × 105 Pa 4.0 × 10–4 m3 300 K 5.0 × 105 Pa 4.0 × 10–4 m3 T initial state final state A change in energy of the gas of 240 J results in an increase of pressure to a final value of 5.0 × 105 Pa at constant volume. The thermodynamic temperature becomes T. Calculate the temperature T, T = K the amount of gas. amount = mol The increase in internal energy ΔU of a system may be represented by the expression ΔU = q + w. State what is meant by the symbol 1. +q, 2. +w. State, for the gas in , the value of 1. ΔU, ΔU = J 2. +q, +q = J 3. +w. +w = J
16. Thermodynamics  →  16.2. The first law of thermodynamics
15. Ideal gases  →  15.2. Equation of state
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3
To demonstrate simple harmonic motion, a student attaches a trolley to two similar stretched springs, as shown in . spring trolley The trolley has mass m of 810 g. The trolley is displaced along the line of the two springs and then released. The subsequent acceleration a of the trolley is given by the expression a = − 2k x m where the spring constant k for each of the springs is 64 N m−1 and x is the displacement of the trolley. Show that the frequency of oscillation of the trolley is 2.0 Hz. The maximum displacement of the trolley is 1.6 cm. Calculate the maximum speed of the trolley. speed = m s−1 The mass of the trolley is increased. The initial displacement of the trolley remains unchanged. Suggest the change, if any, that occurs in the frequency and in the maximum speed of the oscillations of the trolley. frequency: maximum speed:
17. Oscillations  →  17.1. Simple harmonic oscillations
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4
Signals may be transmitted in either analogue or digital form. One advantage of digital transmission is that the signal can be regenerated. Explain what is meant by regeneration, why an analogue signal cannot be regenerated. Digital signals are transmitted along an optic fibre using infra-red radiation. The uninterrupted length of the optic fibre is 58 km. The effective noise level in the receiver at the end of the optic fibre is 0.38 μW. The minimum acceptable signal-to-noise ratio in the receiver is 32 dB. Calculate the minimum acceptable power PMIN of the signal at the receiver. PMIN = W The input signal power to the optic fibre is 9.5 mW. The output power is PMIN. Calculate the attenuation per unit length of the optic fibre. attenuation per unit length = dB km−1
24. Medical physics  →  24.2. Production and use of X-rays
7. Waves  →  7.5. Polarisation
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5
Two small solid metal spheres A and B have equal radii and are in a vacuum. Their centres are 15 cm apart. Sphere A has charge +3.0 pC and sphere B has charge +12 pC. The arrangement is illustrated in . 15 cm 5.0 cm P sphere A charge + 3.0 pC sphere B charge + 12 pC Point P lies on the line joining the centres of the spheres and is a distance of 5.0 cm from the centre of sphere A. Suggest why the electric field strength in both spheres is zero. Show that the electric field strength is zero at point P. Explain your working. Calculate the electric potential at point P. electric potential = V A silver-107 nucleus (107 47 Ag) has speed v when it is a long distance from point P. Use your answer in to calculate the minimum value of speed v such that the nucleus can reach point P. speed = m s−1
18. Electric fields  →  18.5. Electric potential
18. Electric fields  →  18.3. Electric force between point charges
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6
The slew rate of an ideal operational amplifier (op-amp) is said to be infinite. Explain what is meant by infinite slew rate. The circuit of is designed to indicate whether the temperature of the thermistor is above or below 24 °C. 2.00 kΩ 3.00 kΩ R 4.5 V VOUT +5 V + – –5 V The operational amplifier (op-amp) is assumed to be ideal. At 24 °C, the resistance of the thermistor is 1.50 kΩ. Determine the resistance of resistor R such that the output VOUT of the op-amp changes at 24 °C. resistance = Ω On , 1. draw two light-emitting diodes (LEDs) connected so as to indicate whether the output VOUT of the op-amp is either +5 V or −5 V, 2. label with the letter G the LED that will be emitting light when the temperature is below 24 °C. Explain your working.
9. Electricity  →  9.3. Resistance and resistivity
10. D.C. circuits  →  10.3. Potential dividers
10. D.C. circuits  →  10.1. Practical circuits
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7
Explain what is meant by a field of force. State the type of field, or fields, that will give rise to a force acting on a moving uncharged particle, a stationary charged particle, a charged particle moving at an angle to the field or fields. An electron, mass m and charge −q, is moving at speed v in a vacuum. It enters a region of uniform magnetic field of flux density B, as shown in . uniform magnetic field flux density B path of electron mass m, charge –q Initially, the electron is moving at right-angles to the direction of the magnetic field. Explain why the path of the electron in the magnetic field is the arc of a circle. Derive an expression, in terms of the radius r of the path, for the linear momentum of the electron. Show your working.
20. Magnetic fields  →  20.3. Force on a moving charge
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9
State Faraday’s law of electromagnetic induction. The diameter of the cross-section of a long solenoid is 3.2 cm, as shown in . long solenoid coil C 85 turns 3.2 cm I I A coil C, with 85 turns of wire, is wound tightly around the centre region of the solenoid. The magnetic flux density B, in tesla, at the centre of the solenoid is given by the expression B = π × 10−3 × I where I is the current in the solenoid in ampere. Show that, for a current I of 2.8 A in the solenoid, the magnetic flux linkage of the coil C is 6.0 × 10−4 Wb. The current I in the solenoid in is reversed in 0.30 s. Calculate the mean e.m.f. induced in coil C. e.m.f. = mV The current I in the solenoid in is now varied with time t as shown in . 3.0 2.0 1.0 I/ A –1.0 –2.0 –3.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 t / s Use your answer to to show, on , the variation with time t of the e.m.f. E induced in coil C. E / mV 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 t / s
20. Magnetic fields  →  20.4. Magnetic fields due to currents
20. Magnetic fields  →  20.5. Electromagnetic induction
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10
Explain what is meant by the photoelectric effect. One wavelength of electromagnetic radiation emitted from a mercury vapour lamp is 436 nm. Calculate the photon energy corresponding to this wavelength. energy = J Light from the lamp in is incident, separately, on the surfaces of caesium and tungsten metal. Data for the work function energies of caesium and tungsten metal are given in . metal work function energy / eV caesium tungsten 1.4 4.5 Calculate the threshold wavelength for photoelectric emission from caesium, threshold wavelength = nm tungsten. threshold wavelength = nm Use your answers in to state and explain whether the radiation from the mercury lamp of wavelength 436 nm will give rise to photoelectric emission from each of the metals. caesium: tungsten:
22. Quantum physics  →  22.2. Photoelectric effect
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11
Some of the electron energy bands in a solid are illustrated in . forbidden band valence band conduction band (partially filled) The width of the forbidden band and the number of charge carriers occupying each band depends on the nature of the solid. Use band theory to explain why the resistance of a sample of a metal at room temperature changes with increasing temperature.
9. Electricity  →  9.3. Resistance and resistivity
22. Quantum physics  →  22.4. Energy levels in atoms and line spectra
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12
Radon-222 (222 86 Rn) is a radioactive element found in atmospheric air. The decay constant of radon-222 is 2.1 × 10−6 s−1. Define radioactive half-life. Show that the half-life t 1 2 is related to the decay constant λ by the expression λ t 1 2 = 0.693. Radon-222 is considered to be an unacceptable health hazard when the activity of radon-222 is greater than 200 Bq in 1.0 m3 of air. Calculate the minimum mass of radon-222 in 1.0 m3 of air above which the health hazard becomes unacceptable. mass = kg
23. Nuclear physics  →  23.2. Radioactive decay
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