科目：物理 Physics (9702)
年份：2015 夏季
试卷：Paper 41
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, 24: Medical physics, 25: Astronomy and cosmology
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Section A
Answer all the questions in the spaces provided.
1 (a) State Newton’s law of gravitation.
...............................................................................................................................
...............................................................................................................................
............................................................................................................................... [2]
(b) The planet Neptune has eight moons (satellites). Each moon orbits Neptune in a circular path of radius $r$ with a period $T$ .
Assuming that Neptune and each moon behave as point masses, show that $r$ and $T$ are related by the expression
$$
GM_N = \frac{4\pi^2 r^3}{T^2}
$$
where $G$ is the grav5
Use the expression in (b) to determine the ratio
$$
\frac{\text{mass of Neptune}}{\text{mass of Uranus}}
$$
ratio = ………………………………………… [3]
© UCLES 2015 9702/41/M/J/15 [Turn over6 2 (a) State what is meant by *internal energy*. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... [2] (b) The variation with volume $V$ of the pressure $p$ of an ideal gas as it undergoes a cycle ABCA of changes is shown in Fig. 2.1.  Fig. 2.1 The temperature of the gas at A is 290 K. The temperature at B is 870 K. © UCLES 2015 9702/41/M/J/15
7 Determine (i) the amount, in mol, of gas, amount = ………………………………………… mol [2] (ii) the temperature of the gas at C. temperature = ………………………………………… K [2] (c) Explain why the change from C to A involves external work and a change in internal energy. ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… ……………………………………………………………………………………………………… [2] © UCLES 2015 9702/41/M/J/15 [Turn over
8 3 (a) Define specific latent heat. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... [2] (b) An electrical heater is immersed in some melting ice that is contained in a funnel, as shown in Fig. 3.1. <!-- Image: Fig. 3.1 --> Fig. 3.1 The heater is switched on and, when the ice is melting at a constant rate, the mass $m$ of ice
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(i) Complete Fig. 3.2 to determine the mass melted per second for each power of the heater. [2]
(ii) Use the data in the completed Fig. 3.2 to determine
1. a value for the specific latent heat of fusion $L$ of ice,
$$
L = \underline{\hspace{5cm}} \text{ J g}^{-1} \text{ [3]}
$$
2. the rate $h$ of thermal energy gained by the ice from the surroundings.
$$
h = \underline{\hspace{5cm}} \text{ W [2]}
$$
© UCLES 2015 9702/41/M/J/15 [Turn over10 BLANK PAGE © UCLES 2015 9702/41/M/J/15
11 4 (a) For an oscillating body, state what is meant by (i) forced frequency, ....................................................................................................................... ....................................................................................................................... [1] (ii) natural frequency of vibration, ....................................................................................................................... ....................................................................................................................... [1] (iii) resonance. ....................................................................................................................... ...............................................
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5 A charged metal sphere is isolated in space. Measurements of the electric potential $V$ are made for different distances $x$ from the centre of the sphere.
The variation with distance $x$ of the potential $V$ is shown in Fig. 5.1.
Fig. 5.1
(a) Use Fig. 5.1 to determine the electric field strength, in $N\,C^{-1}$ , at a point where $x = 4.0\,\text{cm}$ . Explain your working.
electric field strength = ………………………………………… $N\,C^{-1}$ [3]
(b) The charge on the sphere is $8.0 \times 10^{-9}\,C$ .
(i) Use Fig. 5.1 to state the electric potential at the surface of the sphere.
potential = ………………………………………… V [1]
© UCLES 2015 9702/41/M/J/1513
(ii) The sphere acts as a capacitor. Determine the capacitance of the sphere.
$$
\text{capacitance} = \underline{\hspace{5cm}} \text{ F [2]}
$$
© UCLES 2015 9702/41/M/J/15 [Turn over14
6 (a) State the type of field, or fields, that may cause a force to be exerted on a particle that is
(i) uncharged and moving,
........................................................................................................................... [1]
(ii) charged and stationary,
........................................................................................................................... [1]
(iii) charged and moving at right-angles to the field.
........................................................................................................................... [2]
(b) A particle X has mass $3.32 \times 10^{-26} \, \text{kg}$ and charge $+1.60 \times 10^{-19} \, \text{C}$ .
The particle is travelling in a vacuum with speed $7.60 \times 10^4 \, \text{m} \,15 (ii) calculate the magnetic flux density. magnetic flux density = ………………………………………… T [3] (c) A second particle Y has mass less than that of particle X in (b) and the same charge. It enters the region of uniform magnetic field in (b) with the same speed and along the same initial path as particle X. On Fig. 6.1, draw the path of particle Y in the region of the magnetic field. [1] 7 In many distribution systems for electrical energy, the energy is transmitted using alternating current at high voltages. Suggest and explain an advantage, one in each case, for the use of (a) alternating voltages, ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… ……………………………………………………………………………………………………… [2] (b) high voltages.
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8 A photon of wavelength $6.50 \times 10^{-12} \, \text{m}$ is incident on an isolated stationary electron, as illustrated in Fig. 8.1.
<div style="text-align: center;">
</div>
Fig. 8.1
The photon is deflected elastically by the electron of mass $m_e$ . The wavelength of the deflected photon is $6.84 \times 10^{-12} \, \text{m}$ .
(a) Calculate, for the incident photon,
(i) its momentum,
$$
\text{momentum} = \underline{\hspace{5cm}} \, \text{Ns} \, [2]
$$
(ii) its energy.
$$
\text{energy} = \underline{\hspace{5cm}} \, \text{J} \, [2]
$$
© UCLES 2015 9702/41/M/J/15
Note: The image placeholder (``) is used to represent the diagram in Fig. 8.1 since actual image extraction is not possible. In a real scenario, you would replace this wi17
(b) The angle $\theta$ through which the photon is deflected is given by the expression
$$
\Delta\lambda = \frac{h}{m_e c} (1 - \cos\theta)
$$
where $\Delta\lambda$ is the change in wavelength of the photon, $h$ is the Planck constant and $c$ is the speed of light in free space.
(i) Calculate the angle $\theta$ .
$\theta = \underline{\hspace{5cm}}^\circ$ [2]
(ii) Use energy considerations to suggest why $\Delta\lambda$ must always be positive.
$\underline{\hspace{10cm}}$
$\underline{\hspace{10cm}}$
$\underline{\hspace{10cm}}$ [3]
© UCLES 2015 9702/41/M/J/15 [Turn over18 9 (a) An isotope of an element is radioactive. Explain what is meant by radioactive decay. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... [3] (b) At time $t$ , a sample of a radioactive isotope contains $N$ nuclei. In a short time $\Delta t$ , the number of nuclei that decay is $\Delta N$ . State expressions, in terms of th
19 (c) The variation with time $t$ of the activity $A$ of a sample of a radioactive isotope is shown in Fig. 9.1. Fig. 9.1 The radioactive isotope decays to form a stable isotope S. At time $t = 0$, there are no nuclei of S in the sample. On the axes of Fig. 9.2, sketch a graph to show the variation with time $t$ of the number $n$ of nuclei of S in the sample. Fig. 9.2 [2] © UCLES 2015 9702/41/M/J/15 [Turn over
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Section B
Answer all the questions in the spaces provided.
10 An operational amplifier (op-amp) is used in the comparator circuit of Fig. 10.1.
Fig. 10.1
(a) (i) Show that the potential at the inverting input of the op-amp is +1.0V.
[1]
(ii) Explain why the potential difference across resistor R is +5V when $V_{IN}$ is greater than 1.0V and is zero when $V_{IN}$ is less than 1.0V.
$V_{IN} > 1.0V$: ...............................................................................................................................
.......................................................................................................................................................
$V_{IN} < 1.0V$: .........................................................................................21
(b) The variation with time $t$ of the input voltage $V_{IN}$ is shown in Fig. 10.2.
Fig. 10.2
(i) On the axes of Fig. 10.2, draw the variation with time $t$ of the output potential $V_{OUT}$. [2]
(ii) Suggest a use for this type of circuit.
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............................................................................................................................... [1]
© UCLES 2015 9702/41/M/J/15 [Turn over22 11 (a) State and explain how, in an X-ray tube, the hardness of the X-ray beam is controlled. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... [3] (b) A parallel beam of X-rays has intensity $I_0$ and is incident on a medium having a linear absorption (attenuation) coefficient $\mu$ . (i) State an equation for the variation o
23 12 (a) Information may be carried by means of various channels of communication. Name examples, one in each case, of devices where information is carried to the device using (i) a wire pair, ................................................................................................................... [1] (ii) a coaxial cable, ................................................................................................................... [1] (iii) microwaves. ................................................................................................................... [1] (b) State two advantages of optic fibres as compared with coaxial cables for long-range communication. 1. .......................................................................................