科目：物理 Physics (9702)
年份：2015 冬季
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, 24: Medical physics
4 Section A Answer all the questions in the spaces provided. 1 (a) State Newton’s law of gravitation. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... [2] (b) Some of the planets in the Solar System have several moons (satellites) that have circular orbits about the planet. The planet and each of its moons may be considered to be point masses. Show that the radius $x$ of a moon’s orbit is related to the period $T$ of the orbit by the expression $$ GM =
5
(c) The planet Neptune has eight moons, each in a circular orbit of radius $x$ and period $T$. The variation with $T^2$ of $x^3$ for some of the moons is shown in Fig. 1.1.
<div style="text-align: center;">
</div>
Fig. 1.1
Use Fig. 1.1 and the expression in (b) to determine the mass of Neptune.
$$
\text{mass} = \underline{\hspace{5cm}} \text{ kg [4]}
$$
© UCLES 2015 9702/43/O/N/15 [Turn over6 2 (a) An ideal gas is said to consist of molecules that are hard elastic identical spheres. State two further assumptions of the kinetic theory of gases. 1. ............................................................................................................................... ............................................................................................................................ 2. ............................................................................................................................... ............................................................................................................................ [2] (b) The number of molecules per unit volume in an ideal gas is $n$ . If it is assumed that all the molecules are moving
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(ii) Calculate the mean-square speed of the molecules at $207^\circ \text{C}$ .
$$
\text{mean-square speed} = \underline{\hspace{5cm}} \, \text{m}^2 \text{s}^{-2} \, [2]
$$
© UCLES 2015
9702/43/O/N/15
[Turn over8
3 (a) Two bodies are in thermal equilibrium.
State what is meant by *thermal equilibrium*.
...............................................................................................................................
...............................................................................................................................
............................................................................................................................... [2]
(b) The temperature of a body is found to increase from $15.9^\circ \text{C}$ to $57.2^\circ \text{C}$ .
Determine, in kelvin and to an appropriate number of decimal places,
(i) the rise in temperature of the body,
temperature rise = ................................................... K [1]
(ii) the final te9
4 (a) Define simple harmonic motion.
...............................................................................................................................
...............................................................................................................................
............................................................................................................................... [2]
(b) A tube, sealed at one end, has a circular cross-sectional area $A$ of $4.9 \times 10^{-4} \, \text{m}^2$ . Some sand is put in the tube so that the total mass $M$ of the tube and its contents is 70 g. The tube floats upright in a liquid, as shown in Fig. 4.1.
Fig. 4.1
The liquid has a density $\rho$ of $0.79 \, \text{g} \, \text{cm}^{-3}10
(c) The tube in (b) is displaced vertically and then released. The variation with time $t$ of the distance $h$ is shown in Fig. 4.2.
<div style="text-align: center;">
</div>
Fig. 4.2
The system oscillates with simple harmonic motion of angular frequency $\omega$ given by the expression
$$
\omega^2 = \frac{\rho A g}{M}
$$
where $g$ is the acceleration of free fall.
(i) Use data from (b) to determine
1. the time $t_1$ ,
$t_1 = \text{................................................... s [3]}$
2. the time $t_3$ .
$t_3 = \text{................................................... s [1]}$
© UCLES 2015 9702/43/O/N/1511 (ii) Determine the loss in total energy of the oscillating system between time $t = 0$ and time $t = t_4$. loss in energy = ………………………………………… J [3] © UCLES 2015 9702/43/O/N/15 [Turn over
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5 A positively charged solid metal sphere is isolated in space. The electric field strength $E$ is measured for different distances $x$ from the centre of the sphere. The variation with $x$ of the field strength $E$ is shown in Fig. 5.1.
Fig. 5.1
(a) Suggest why, for values of $x$ less than 4.0 cm, the electric field strength is zero.
...............................................................................................................................
...............................................................................................................................
............................................................................................................................... [2]
(b) A point charge of $+8.5 \times 10^{-9}13
6 Suggest an explanation for each of the following observations.
(a) Two wires are laid side-by-side and carry equal currents $I$ in opposite directions, as shown in Fig. 6.1.
$\begin{array}{c} \text{Fig. 6.1} \\ \end{array}$
The total magnetic flux density due to the current in the wires is negligible.
...............................................................................................................................
...............................................................................................................................
...............................................................................................................................
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7 A student is using a power supply that produces a sinusoidal output. The meters on the supply show that the output voltage $V$ has a root-mean-square (r.m.s.) value of 14 V with a frequency of 750 Hz.
The variation with time $t$ of the output voltage $V$ may be represented by the expression
$$
V = V_0 \sin \omega t.
$$
(a) Determine the value of
(i) $V_0$ ,
$$
V_0 = \underline{\hspace{5cm}} \text{ V [1]}
$$
(ii) $\omega$ .
$$
\omega = \underline{\hspace{5cm}} \text{ rad s}^{-1} \text{ [1]}
$$
(b) A capacitor with a large capacitance is connected across the terminals of the supply.
Suggest and explain why this may lead to a large current from the supply.
$\underline{\hspace{10cm}}$
$\underline{\hspace{10cm}}$
$\underline{\hspace{10cm}}$ [3]
© UCLES 2015
9702/43/O/N/1515
8 Light of wavelength $\lambda$ is incident on a metal surface having a work function energy $\varphi$ . Photoelectrons of maximum kinetic energy $E_{\text{MAX}}$ are emitted from the surface.
(a) State an equation relating $\varphi$ , $E_{\text{MAX}}$ and $\lambda$ . Explain any other symbols you use.
...............................................................................................................................
...............................................................................................................................
............................................................................................................................... [2]
(b) The variation with $1/\lambda$ of $E_{\text{MAX}}$ is shown in Fig. 8.1.
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9 (a) State what is meant by the *binding energy* of a nucleus.
...............................................................................................................................
...............................................................................................................................
............................................................................................................................... [2]
(b) Data for two isotopes of uranium are given in Fig. 9.1.
<table>
<tr>
<th>isotope</th>
<th>binding energy per nucleon/MeV</th>
<th>binding energy/MeV</th>
</tr>
<tr>
<td>uranium-235</td>
<td>7.59</td>
<td>...........................................</td>
</tr>
<tr>
<td>uranium-238</td>
<td>....17 (ii) A sample of uranium-235 has an activity of $5.0 \times 10^3$ Bq. Calculate the mass of the sample. mass = ………………………………………… g [3] © UCLES 2015 9702/43/O/N/15 [Turn over
18 BLANK PAGE © UCLES 2015 9702/43/O/N/15
19
Section B
Answer all the questions in the spaces provided.
10 The output potential $V_{OUT}$ from an operational amplifier is to be monitored using an output device. The output $V_{OUT}$ can be either +5V or –5V.
(a) On Fig. 10.1, draw a circuit for the output device that consists of two light-emitting diodes B and G. Diode B alone is to emit light when $V_{OUT}$ is +5V. Diode G alone is to emit light when $V_{OUT}$ is –5V.
$V_{OUT}$ ○—————————————————————————
○————●—————————————————————————
Fig. 10.1
[3]
(b) On Fig. 10.2, draw a circuit of the output device that consists of a relay and a diode such that a high-power lamp is switched on only when $V_{OUT}$ is –5V.
$V_{OUT}$ ○—————
○————●—————
=
high power lamp
power supply
Fig. 10.2
[4]
© UCLES 2015 9702/43/O/N/15 [T20 11 (a) An X-ray source is placed on one side of a metal plate, as shown in Fig. 11.1. Fig. 11.1 The intensity of the X-ray beam is measured at points A and B. State two reasons, other than absorption of X-ray photons in the metal, for the intensity at point A to be different to that at point B. 1. ............................................................................................................................... ............................................................................................................................ 2. ............................................................................................................................... ..........................................................................................................
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(i) Calculate the ratio
$$
\frac{\text{intensity of X-ray beam incident on the specimen}}{\text{intensity of X-ray beam emerging from the specimen}}
$$
for the beam passing through
1. the 4.0 cm thickness of muscle alone,
ratio = ………………………………………… [2]
2. the bone and the muscle.
ratio = ………………………………………… [2]
(ii) Using your answers in (i), suggest and explain whether an X-ray image of this specimen is likely to have good contrast.
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
……………………………………………………………………………………………………… [2]
© UCLES 2015 9702/43/O/N/15 [Turn over22 12 A transmission system for speech may be represented by the block diagram of Fig. 12.1.  Fig. 12.1 (a) Name the component labelled (i) block X, ................................................................................................................... [1] (ii) block Y, ................................................................................................................... [1] (iii) Z. ................................................................................................................... [1] (b) The variation with time of part of the signal at the input P to the analogue-to-digital converter (ADC) is shown in Fig. 12.2.  Fig. 12.2 © UCLES 2015 9702/43/O/N/15
23 Each number of the output from the ADC is a digital number where the smallest bit represents 1 mV. State (i) the minimum number of bits in each digital number so that the signal in Fig. 12.2 can be sampled fully, number = ………………………………………… [1] (ii) the digital number produced by the ADC at time 0.50 ms. number = ………………………………………… [1] (c) The ADC samples the signal in Fig. 12.2 at a frequency of 4.0 kHz. The first sample is taken at time zero. Using data from Fig. 12.2, draw, on the axes of Fig. 12.3, the variation with time of the output at point Q for time zero to time 1.5 ms.  Fig. 12.3 [4] Please turn over for Question 13. © UCLES 2015 9702/43/O/N/15 [Turn over