科目：物理 Physics (9702)
年份：2018 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
4 Answer all the questions in the spaces provided. 1 (a) State Newton’s law of gravitation. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... [2] (b) A distant star is orbited by several planets. Each planet has a circular orbit with a different radius. (i) Each planet orbits at constant speed. Explain whether the planets are
5
1. Show that the constant $k$ is given by the expression
$$
k = \frac{GM}{4\pi^2}
$$
where $G$ is the gravitational constant and $M$ is the mass of the star.
[3]
2. Use data from Fig. 1.1 for the three planets and the expression for $k$ to calculate the mass $M$ of the star.
$M = \underline{\hspace{5cm}} \text{kg [3]}$
[Total: 9]
© UCLES 2018 9702/41/M/J/18 [Turn over6 2 A metal plate is made to vibrate vertically by means of an oscillator, as shown in Fig. 2.1. <div style="text-align: center;">  <br/> Fig. 2.1 </div> Some sand is sprinkled on to the plate. The variation with displacement $y$ of the acceleration $a$ of the sand on the plate is shown in Fig. 2.2. <div style="text-align: center;">  <br/> Fig. 2.2 </div> (a) (i) Use Fig. 2.2 to show how it can be deduced that the sand is undergoing simple harmonic motion. ............................................................................................................................... ............................................................................................................................... ....................
7 (ii) Calculate the frequency of oscillation of the sand. frequency = ………………………………………… Hz [2] (b) The amplitude of oscillation of the plate is gradually increased beyond 8 mm. The frequency is constant. At one amplitude, the sand is seen to lose contact with the plate. For the plate when the sand first loses contact with the plate, (i) state the position of the plate, ……………………………………………………………………………………………………… [1] (ii) calculate the amplitude of oscillation. amplitude = ………………………………………… mm 3 © UCLES 2018 9702/41/M/J/18 [Turn over
8 3 (a) (i) State what is meant by the *internal energy* of a system. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... [2] (ii) Explain why, for an ideal gas, the change in internal energy is directly proportional to the change in thermodynamic temperature of the gas. .............................................................
9 4 Piezo-electric transducers are used for the generation of ultrasonic waves. (a) State one other use, apart from in ultrasound, of piezo-electric transducers. ............................................................................................................................[1] (b) Explain the main principles behind the use of ultrasound to obtain diagnostic information about internal body structures. ............................................................................................................................ ............................................................................................................................ ............................................................................................................................ .
10 5 A geostationary satellite orbits the Earth with a period of 24 hours. (a) State (i) the direction of the orbit about the Earth, ...................................................................................................................[1] (ii) the position of the satellite relative to the Earth’s surface, ...................................................................................................................[1] (iii) a typical frequency for communication between the satellite and Earth. frequency = ........................................................................ Hz [1] (b) A signal transmitted from Earth to a satellite has an initial power of 3.0 kW. The signal power received by the satellite is attenuated by 195 dB. (i) Calculate the signal powe
11
6 (a) State what is meant by *electric field strength*.
...............................................................................................................................
............................................................................................................................... [1]
(b) An isolated metal sphere A of radius 26cm is positively charged. Sphere A is shown in Fig. 6.1.
<div style="text-align: center;">
<br/>
Fig. 6.1
</div>
Electrical breakdown (a spark) occurs when the electric field strength at the surface of the sphere exceeds $2.0 \times 10^4 \, \text{V} \, \text{m}^{-1}$ .
Calculate the maximum charge $Q$ that can be stored on the sphere.
$$
Q = \underline{\hspace{5cm}} \, \text{C} \, [2]
$$
(c) 12 7 (a) Explain what is meant by the *capacitance* of a parallel plate capacitor. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... [3] (b) A parallel plate capacitor C is connected into the circuit shown in Fig. 7.1. <div style="text-align: center;">  <br/> Fig. 7.1 </div> When switch S is at positio
13 (ii) the charge on one plate of the capacitor, each time that it is charged, charge = ………………………………………… C [1] (iii) the capacitance of capacitor C. capacitance = ………………………………………… F [2] (c) A second capacitor, having a capacitance equal to that of capacitor C, is now placed in series with C. Suggest and explain the effect on the current recorded on the ammeter. ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… ……………………………………………………………………………………………………… 2 © UCLES 2018 9702/41/M/J/18 [Turn over
14 8 (a) Negative feedback is often used in amplifiers incorporating an operational amplifier (op-amp). State (i) what is meant by *negative feedback*, ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... [2] (ii) two effects of negative feedback on the gain of an amplifier. 1. ............................................................................................................................... .....................................................
15
(ii) Determine the output potential difference $V_{OUT}$ for input potential differences $V_{IN}$ of
1. $-0.10\,V$,
$$
V_{OUT} = \underline{\hspace{5cm}}\,V
$$
2. $+1.3\,V$.
$$
V_{OUT} = \underline{\hspace{5cm}}\,V
$$
[2]
(iii) The gain of the amplifier shown in Fig. 8.1 is constant.
State one change that can be made to the circuit of Fig. 8.1 so that the amplifier circuit monitors light intensity levels, with the magnitude of the gain decreasing as light intensity increases.
$\underline{\hspace{10cm}}$
$\underline{\hspace{10cm}}$ [1]
[Total: 9]
© UCLES 2018 9702/41/M/J/18 [Turn over16
9 A rigid copper wire is held horizontally between the pole pieces of two magnets, as shown in Fig. 9.1.
<div style="display: flex; justify-content: space-between;">
<div style="text-align: center;">
<br>
side view
</div>
<div style="text-align: center;">
<br>
top view
</div>
</div>
Fig. 9.1
The width of each pole piece is 8.5 cm.
The uniform magnetic flux density $B$ in the region between the poles of the magnets is 3.7 mT and is zero outside this region.
The angle between the wire and the direction of the magnetic field is $\theta$ .
The current in the wire is in the direction shown on Fig. 9.1.
(a) By reference to the side view of Fig. 9.1, state and explain the direction of the force on the magnets.
....17
(ii) The angle $\theta$ is changed to $60^\circ$ .
The length of wire in the magnetic field is $\left(\frac{8.5}{\sin 60^\circ}\right)$ cm.
Calculate the force on the wire.
force = ………………………………………… N [1]
(c) The constant current in the wire is now changed to an alternating current of frequency $20$ Hz and root-mean-square (r.m.s.) value $5.1$ A.
The angle between the wire and the direction of the magnetic field is $90^\circ$ .
On Fig. 9.2, sketch a graph to show the variation with time $t$ of the force $F$ on the wire for two cycles of the alternating current.
Fig. 9.2
3
© UCLES 2018 9702/41/M/J/18 [Turn over18 10 (a) State Faraday’s law of electromagnetic induction. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... [2] (b) A coil of insulated wire is wound on to one end of a ferrous core and connected to a battery, as shown in Fig. 10.1.  Fig. 10.1 An aluminium ring is placed on the core. The ring can move fre
19 11 (a) (i) Explain what is meant by a *photon*. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... [2] (ii) By reference to intensity of light, state one piece of evidence provided by the photoelectric effect for a particulate nature of light. ............................................................................................................................... .....................................................................................
20
12 An X-ray beam is used to produce an image of a model of a thumb.
A parallel beam of X-ray radiation of intensity $I_0$ is incident on the model, as illustrated in Fig. 12.1.
<div style="text-align: center;">
</div>
Fig. 12.1
Data for the attenuation (absorption) coefficient $\mu$ in bone and in soft tissue are shown in Fig. 12.2.
<table>
<tr>
<th></th>
<th> $\mu/\text{cm}^{-1}$ </th>
</tr>
<tr>
<td>bone</td>
<td>3.0</td>
</tr>
<tr>
<td>soft tissue</td>
<td>0.90</td>
</tr>
</table>
Fig. 12.2
(a) Calculate, in terms of the incident intensity $I_0$ of the X-ray beam, the intensity of the beam after passing through
(i) a thickness of 2.8 cm of soft tissue,
$$
\text{intensity} = \underline{\hspace{5cm}} I_0 \text{ [2]}21 (ii) the bone and soft tissue, as shown in Fig. 12.1. intensity = ………………………………………… $I_0$ [2] (b) (i) State what is meant by the contrast of an X-ray image. ……………………………………………………………………………………………………… [2] (ii) By reference to your answers in (a), suggest whether the X-ray image of the model has good contrast. ……………………………………………………………………………………………………… [1] [Total: 7] © UCLES 2018 9702/41/M/J/18 [Turn over
22 13 (a) State what is meant by radioactive decay. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... [2] (b) The variation with time $t$ of the number $N$ of technetium-101 nuclei in a sample of radioactive material is shown in Fig. 13.1.  Fig. 13.1 © UCLES 2018 9702/41/M/J/18
23
(i) Use Fig. 13.1 to determine the activity, in Bq, of the sample of technetium-101 at time $t = 14.0$ minutes. Show your working.
activity = ………………………………………… Bq [4]
(ii) Without calculating the half-life of technetium-101, use your answer in (i) to determine the decay constant $\lambda$ of technetium-101.
$\lambda = \text{……………………………………… s}^{-1} \text{ [2]}$
[Total: 8]
© UCLES 2018 9702/41/M/J/18