9702_w13_qp_43
A paper of Physics, 9702
Questions:
12
Year:
2013
Paper:
4
Variant:
3
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1
State Newton’s law of gravitation. A star and a planet are isolated in space. The planet orbits the star in a circular orbit of radius R, as illustrated in . star mass M R planet t The angular speed of the planet about the star is ω. By considering the circular motion of the planet about the star of mass M, show that ω and R are related by the expression R 3ω2 = GM where G is the gravitational constant. Explain your working. For Examiner’s Use The Earth orbits the Sun in a circular orbit of radius 1.5 × 108 km. The mass of the Sun is 2.0 × 1030 kg. A distant star is found to have a planet that has a circular orbit about the star. The radius of the orbit is 6.0 × 108 km and the period of the orbit is 2.0 years. Use the expression in to calculate the mass of the star. mass = kg
13. Gravitational fields  →  13.3. Gravitational field of a point mass
13. Gravitational fields  →  13.2. Gravitational force between point masses
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2
For Examiner’s Use State what is meant by the internal energy of a system. Explain why, for an ideal gas, the internal energy is equal to the total kinetic energy of the molecules of the gas. The mean kinetic energy of a molecule of an ideal gas is given by the expression = 3 2kT where k is the Boltzmann constant and T is the thermodynamic temperature of the gas. A cylinder contains 1.0 mol of an ideal gas. The gas is heated so that its temperature changes from 280 K to 460 K. Calculate the change in total kinetic energy of the gas molecules. change in energy = J For Examiner’s Use During the heating, the gas expands, doing 1.5 × 103 J of work. State the first law of thermodynamics. Use the law and your answer in to determine the total energy supplied to the gas. total energy = J
16. Thermodynamics  →  16.2. The first law of thermodynamics
16. Thermodynamics  →  16.1. Internal energy
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3
For Examiner’s Use Define electric potential at a point. Two point charges A and B are separated by a distance of 20 nm in a vacuum, as illustrated in . A P B x 20 nm A point P is a distance x from A along the line AB. The variation with distance x of the electric potential VA due to charge A alone is shown in . 0.2 0.4 0.6 0.8 potential V / V x / nm VA VB The variation with distance x of the electric potential VB due to charge B alone is also shown in . For Examiner’s Use State and explain whether the charges A and B are of the same, or opposite, sign. By reference to , state how the combined electric potential due to both charges may be determined. Without any calculation, use to estimate the distance x at which the combined electric potential of the two charges is a minimum. x = nm The point P is a distance x = 10 nm from A. An α-particle has kinetic energy EK when at infinity. Use to determine the minimum value of EK such that the α-particle may travel from infinity to point P. EK = J
18. Electric fields  →  18.5. Electric potential
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4
For Examiner’s Use State two functions of capacitors connected in electrical circuits. 1. 2. Three capacitors are connected in parallel to a power supply as shown in . V C1 C3 C2 The capacitors have capacitances C1, C2 and C3. The power supply provides a potential difference V. Explain why the charge on the positive plate of each capacitor is different. Use your answer in to show that the combined capacitance C of the three capacitors is given by the expression C = C1 + C2 + C3. For Examiner’s Use A student has available three capacitors, each of capacitance 12 μF. Draw circuit diagrams, one in each case, to show how the student connects the three capacitors to provide a combined capacitance of 8 μF, 18 μF.
19. Capacitance  →  19.1. Capacitors and capacitance
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5
For Examiner’s Use A uniform magnetic field of flux density B makes an angle θ with a flat plane PQRS, as shown in . e e e e P Q S R magnetic field flux density B The plane PQRS has area A. State what is meant by a magnetic field, an expression, in terms of A, B and θ, for the magnetic flux Φ through the plane PQRS. A vertical aluminium window frame DEFG has width 52 cm and length 95 cm, as shown in . hinge hinge 52 cm D G E F 95 cm The frame is hinged along the vertical edge DG. The horizontal component BH of the Earth’s magnetic field is 1.8 × 10–5 T. For the closed window, the frame is normal to the horizontal component BH. The window is opened so that the plane of the window rotates through 90°. For Examiner’s Use Explain why, when the window is opened, the change in magnetic flux linkage due to the vertical component of the Earth’s magnetic field is zero. Calculate, for the window opening through an angle of 90°, the change in magnetic flux linkage. change in flux linkage = Wb State Faraday’s law of electromagnetic induction. The window in is opened in a time of 0.30 s. Use your answer in to calculate the average e.m.f. induced in the window frame. e.m.f. = V State the sides of the window frame between which the e.m.f. is induced. between side and side
20. Magnetic fields  →  20.5. Electromagnetic induction
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6
For Examiner’s Use A particle has mass m and charge +q and is travelling with speed v through a vacuum. The initial direction of travel is parallel to the plane of two charged horizontal metal plates, as shown in . + V path of particle metal plate metal plate The uniform electric field between the plates has magnitude 2.8 × 104 V m–1 and is zero outside the plates. The particle passes between the plates and emerges beyond them, as illustrated in . Explain why the path of the particle in the electric field is not an arc of a circle. A uniform magnetic field is now formed in the region between the metal plates. The magnetic field strength is adjusted so that the positively charged particle passes undeviated between the plates, as shown in . + V path of particle path of particle region of uniform electric and magnetic fields For Examiner’s Use State and explain the direction of the magnetic field. The particle has speed 4.7 × 105 m s–1. Calculate the magnitude of the magnetic flux density. Explain your working. magnetic fl ux density = T The particle in has mass m, charge +q and speed v. Without any further calculation, state the effect, if any, on the path of a particle that has mass m, charge –q and speed v, mass m, charge +q and speed 2v, mass 2m, charge +q and speed v.
20. Magnetic fields  →  20.3. Force on a moving charge
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7
For Examiner’s Use By reference to the photoelectric effect, explain what is meant by work function energy, why, even when the incident light is monochromatic, the emitted electrons have a range of kinetic energy up to a maximum value. Electromagnetic radiation of frequency f is incident on a metal surface. The variation with frequency f of the maximum kinetic energy EMAX of electrons emitted from the surface is shown in . f / 1015 Hz EMAX / 10 –18 J For Examiner’s Use Use to determine the work function energy of the metal surface. work function energy = J A second metal has a greater work function energy than that in . On , draw a line to show the variation with f of EMAX for this metal. Explain why the graphs in and do not depend on the intensity of the incident radiation.
22. Quantum physics  →  22.2. Photoelectric effect
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8
For Examiner’s Use One possible nuclear fission reaction is 92 U + 1 0 n 56 Ba + 92 36 Kr + 3 1 0 n + energy. Barium-141 (141 56 Ba) and krypton-92 (92 36 Kr) are both β-emitters. Barium-141 has a half-life of 18 minutes and a decay constant of 6.4 × 10–4 s–1. The half-life of krypton-92 is 3.0 seconds. State what is meant by decay constant. A mass of 1.2 g of uranium-235 undergoes this nuclear reaction in a very short time (a few nanoseconds). Calculate the number of barium-141 nuclei that are present immediately after the reaction has been completed. number = Using your answer in , calculate the total activity of the barium-141 and the krypton-92 a time of 1.0 hours after the fission reaction has taken place. activity = Bq
11. Particle physics  →  11.1. Atoms, nuclei and radiation
23. Nuclear physics  →  23.2. Radioactive decay
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9
State three properties of an ideal operational amplifier (op-amp). 1. 2. 3. An amplifier circuit is shown in . – + +9 V –9 V V IN V OUT 10.8 k1 1.2 k1 Calculate the gain of the amplifier circuit. gain = For Examiner’s Use The variation with time t of the input potential VIN is shown in . –10 – 5 potential / V t V IN On the axes of , show the variation with time t of the output potential VOUT .
10. D.C. circuits  →  10.1. Practical circuits
10. D.C. circuits  →  10.3. Potential dividers
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11
For Examiner’s Use 11 Data may be transmitted in either analogue or digital form. State what is meant by a digital signal, three advantages of the digital transmission of data when compared to analogue transmission. 1. 2. 3. The block diagram of represents the digital transmission of music. parallel- to-serial converter serial-to- parallel converter ADC Y X Y State the name of 1. the blocks labelled Y, 2. the block labelled X. Describe the function of the parallel-to-serial converter.
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12
For Examiner’s Use 12 State two reasons why frequencies in the gigahertz (GHz) range are used in satellite communication. 1. 2. In one particular satellite communication system, the frequency of the signal transmitted from Earth to the satellite (the up-link) is 6 GHz. The frequency of the signal transmitted back to Earth from the satellite (the down-link) is 4 GHz. Explain why the two signals are transmitted at different frequencies. A signal transmitted from Earth has a power of 3.1 kW. This signal, received by a satellite, has been attenuated by 185 dB. Calculate the power of the signal received by the satellite. power = W
13. Gravitational fields  →  13.2. Gravitational force between point masses
8. Superposition  →  8.3. Interference
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