科目：物理 Physics (9702)
年份：2025 夏季
试卷：Paper 43
总页数：20
章节：12-13: Circular Motion & Gravitational Fields, 14-16: Temperature, Ideal Gases & Thermodynamics, 17: Oscillations, 18: Electric fields, 19: Capacitance, 20: Magnetic fields, 21: Alternating currents, 22: Quantum physics, 23: Nuclear physics, 25: Astronomy and cosmology
*0000800000004* DFD 4 1 (a) Define gravitational potential at a point. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... [2] (b) Mars is a planet that may be considered to be an isolated uniform sphere of radius $3.4 \times 10^6$ m. A satellite of mass 122 kg is in orbit around Mars at a constant height of $1.7 \times 10^6$ m above the surface of the planet. The height of the orbit is increased to $6.8 \times 10^6$ m above the surface. This increases th
*0000800000005* DFD 5 (c) The satellite in (b) is moved to an orbit in which the satellite remains at the same point above the surface of Mars. (i) The orbit has a period of 25 hours. State what can be deduced from this about the rotation of Mars on its axis. ............................................................................................................................... ............................................................................................................................... [1] (ii) State one other feature of this orbit. ............................................................................................................................... ..................................................................................................
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2 A helium atom may be modelled as a nucleus surrounded by two electrons in diametrically opposite circular orbits, each of radius 170 pm, as shown in Fig. 2.1.
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Fig. 2.1
(a) State Coulomb’s law.
...............................................................................................................................
...............................................................................................................................
............................................................................................................................... [2]
(b) (i) State the charge on the nucleus, in terms of the elementary charge $e$ .
charge = ...........................*0000800000007*
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(c) Assume that the force in (b)(ii) is the only force on the electrons.
(i) Calculate the speed of the orbiting electrons.
speed = ………………………………………… m s⁻¹ [2]
(ii) Calculate the period of the orbit of the electrons.
period = ………………………………………… s [2]
(d) In practice, the orbit of each electron is affected by the presence of the other electron.
(i) For the position of one of the electrons, determine the ratio
$\frac{\text{electric field strength due to the other electron}}{\text{electric field strength due to the nucleus}}$
ratio = ………………………………………… [2]
(ii) Use your answer in (d)(i) to suggest and explain how the orbit of the electron is affected by the presence of the other electron.
…………………………………………………………………………………………………………
………………………………………………………………………………………*0000800000008* DFD 8 3 (a) Define specific latent heat. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... [2] (b) Explain why, for a substance, the specific latent heat of vaporisation is usually greater than the specific latent heat of fusion. ............................................................................................................................... ...................................................................................
*0000800000009* DFD 9 4 (a) (i) State what is meant by the internal energy of a system. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... [2] (ii) Explain why the internal energy of an ideal gas is directly proportional to the thermodynamic temperature of the gas. ............................................................................................................................... ................................................................
*0000800000010* DFD 10 5 A cuboidal block floats in a liquid with its base horizontal, as shown in Fig. 5.1.  Fig. 5.1 The base of the block is at a depth $h$ below the surface of the liquid. The block is displaced downwards by a small distance and then released so that it oscillates. Fig. 5.2 shows the variation with $h$ of the acceleration $a$ of the block.  Fig. 5.2 Fig. 5.3 shows the variation with $h$ of the kinetic energy $E_K$ of the block.  Fig. 5.3 © UCLES 2025 9702/43/M/J/25 DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN
*0000800000011* DFD 11 (a) (i) Determine the amplitude of the oscillations. amplitude = ………………………………………… m [1] (ii) State what the line in Fig. 5.2 shows about the nature of the oscillations. ……………………………………………………………………………………………………… [1] (b) State three other quantitative conclusions that can be drawn from Fig. 5.2 and Fig. 5.3 about the block and its oscillations. Use the space for any working. 1 ……………………………………………………………………………………………………… …………………………………………………………………………………………………… 2 ……………………………………………………………………………………………………… …………………………………………………………………………………………………… 3 ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… [3] (c) On Fig. 5.4, sketch the variation with $h$ of the potential energy $E_p$ of the oscillations.  Fig. 5.4 3 © UCLE
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6 Fig. 6.1 shows a circuit that rectifies an alternating input voltage $V_{IN}$ and produces an output voltage $V_{OUT}$ across a resistor R.
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Fig. 6.1
The four terminals of the rectification circuit are labelled W, X, Y and Z.
A capacitor C is connected in parallel with resistor R.
(a) (i) State what is meant by rectification.
............................................................................................................................ [1]
(ii) State the purpose of capacitor C.
............................................................................................................................ [1]
(b) Fig. 6.2 shows the variations with time $t$ of the potential differen*0000800000013*
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(i) The variation of $V_{IN}$ with $t$ can be represented by
$$
V_{IN} = A \cos Bt
$$
where $A$ and $B$ are constants.
Determine the values of $A$ and $B$ . Give a unit with your answer for $A$ .
$A =$ ………………………………………… unit ………………
$B =$ ………………………………………… rad s⁻¹ [2]
(ii) Determine the type of rectification produced by the circuit in Fig. 6.1.
……………………………………………………………………………………………………… [1]
(iii) On Fig. 6.3, draw the circuit diagram for the components inside the rectification circuit.
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Fig. 6.3
[2]
(iv) Determine a value for the time constant for the discharge of the capacitor $C$ through the resistor $R$ in Fig. 6.1.
time constant = ………………………………………… s [3]
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(c) The capacitor C has a capacitance of $570\,\mu\mathrm{F}$ .
Use your answer in (b)(iv) to determine the resistance of resistor R.
resistance = ………………………………………… $\Omega$ 2
7 (a) Define magnetic flux density.
………………………………………………………………………………………………………
………………………………………………………………………………………………………
……………………………………………………………………………………………………… [2]
(b) A particle of mass $m$ and charge $+Q$ moves at speed $v$ into a region where there is a uniform magnetic field, as shown in Fig. 7.1.
Fig. 7.1
The uniform magnetic field is into the page and has flux density $B$ . The particle enters the region of the field at point Y.
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(i) State an expression, in terms of some or all of $m$, $Q$, $B$ and $v$, for the magnetic force $F$ that acts on the particle when it is at point Y.
$$
F = \text{...................................................} [1]
$$
(ii) On Fig. 7.1, draw an arrow at point Y to indicate the direction of the force in (b)(i). [1]
(iii) On Fig. 7.1, draw a line to show a possible path for the particle through the region of the magnetic field. [1]
(c) (i) Explain how an electric field can be used with the magnetic field to ensure that the particle in (b) now passes through point Z.
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8 (a) State what is meant by the de Broglie wavelength.
...............................................................................................................................
............................................................................................................................... [1]
(b) Calculate the de Broglie wavelength of an electron moving at a speed of $4.9 \times 10^7 \, \text{m} \, \text{s}^{-1}$ .
wavelength = ................................................... m [2]
(c) State one similarity and one difference between an electron and a positron.
similarity: ...............................................................................................................................
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(iii) Explain why two gamma-ray photons are produced, rather than just one.
...............................................................................................................................
............................................................................................................................... [1]
(iv) Show that the kinetic energy of the electron before the collision is $1.1 \times 10^{-15}$ J.
[1]
(v) Use the information in (d)(iv) to determine, to three significant figures, the wavelength associated with the gamma radiation emitted in the collision.
wavelength = ................................................... m 3
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DO*0000800000018* DFD 18 9 (a) Define activity of a radioactive sample. ............................................................................................................................... ............................................................................................................................... [1] (b) Explain why the variation with time of the activity of a radioactive sample is exponential in nature. ............................................................................................................................ ............................................................................................................................ .........................................................................................................
*0000800000019* DFD 19 (iii) On Fig. 9.1, sketch the variation of the activity $A$ of the sample with $t$ for values of $t$ between $t = 0$ and $t = 24$ min.  Fig. 9.1 3 © UCLES 2025 9702/43/M/J/25 [Turn over] DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN
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10 (a) State Hubble’s law.
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(b) A star in a distant galaxy emits radiation that has a maximum intensity of emission at a wavelength of $4.62 \times 10^{-7}$ m.
Observations of the galaxy made on the Earth detect the maximum intensity of emission from the star at a wavelength of $4.91 \times 10^{-7}$ m.
(i) Explain why the observed wavelength and the emitted wavelength have diffe*0000800000021*
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(c) A value for the Hubble constant is $2.3 \times 10^{-18} \, \text{s}^{-1}$ .
Use your answer in (b)(ii) to determine the distance of the star in (b) from the Earth.
distance = ………………………………………… m 2
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