科目：物理 Physics (9702)
年份：2011 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, 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. For Examiner's Use 1 (a) Newton’s law of gravitation applies to point masses. (i) State Newton’s law of gravitation. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... [2] (ii) Explain why, although the planets and the Sun are not point masses, the law also applies to planets orbiting the Sun. .....................................................................................................
5 2 (a) State what is meant by the Avogadro constant $N_A$ . ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... [2] (b) A balloon is filled with helium gas at a pressure of $1.1 \times 10^5$ Pa and a temperature of $25^\circ$ C. The balloon has a volume of $6.5 \times 10^4$ cm³. Helium may be assumed to be an ideal gas. Determine the number of gas atoms in the balloon. number = ................................................... [4] For Examiner’s Use
6
3 (a) Define simple harmonic motion.
...............................................................................................................................
...............................................................................................................................
............................................................................................................................... [2]
(b) A tube, sealed at one end, has a total mass $m$ and a uniform area of cross-section $A$ . The tube floats upright in a liquid of density $\rho$ with length $L$ submerged, as shown in Fig. 3.1a.
<div style="display: flex; justify-content: space-between;">
<div style="text-align: center;">
<br>
Fig. 3.1a
</div>
<div style="text7
(i) Explain how it can be deduced from the expression that the tube is moving with simple harmonic motion.
...............................................................................................................................
...............................................................................................................................
............................................................................................................................... [2]
(ii) The tube, of area of cross-section $4.5 \, \text{cm}^2$ , is floating in water of density $1.0 \times 10^3 \, \text{kg} \, \text{m}^{-3}$ .
Calculate the mass of the tube that would give rise to oscillations of frequency 1.5 Hz.
mass = ........................................... g [4]
For 8 4 (a) Define *electric potential* at a point. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... [2] (b) Two small spherical charged particles P and Q may be assumed to be point charges located at their centres. The particles are in a vacuum. Particle P is fixed in position. Particle Q is moved along the line joining the two charges, as illustrated in Fig. 4.1. particle P $\leftarrow x \rightarrow$ particle Q Fig. 4.1 The variation with separation $x
9
(ii) Use your answer in (i) to show that the force on particle Q is proportional to the gradient of the curve of Fig. 4.2.
...............................................................................................................................
...............................................................................................................................
............................................................................................................................... [2]
(c) The magnitude of the charge on each of the particles P and Q is $1.6 \times 10^{-19} \, \text{C}$ . Calculate the separation of the particles at the point where particle Q has electric potential energy equal to $-5.1 \, \text{eV}$ .
separation = ...............................10
5 (a) State what is meant by a *magnetic field*.
...............................................................................................................................
...............................................................................................................................
............................................................................................................................... [2]
(b) A charged particle of mass $m$ and charge $+q$ is travelling with velocity $v$ in a vacuum. It enters a region of uniform magnetic field of flux density $B$ , as shown in Fig. 5.1.
<div style="text-align: center;">
<br/>
<strong>Fig. 5.1</strong>
</div>
The magnetic field is normal to the direction of motion of th11
(c) A thin metal foil is placed in the magnetic field in (b).
A second charged particle enters the region of the magnetic field. It loses kinetic energy as it passes through the foil. The particle follows the path shown in Fig. 5.2.
<div style="text-align: center;">
<br/>
Fig. 5.2
</div>
(i) On Fig. 5.2, mark with an arrow the direction of travel of the particle. [1]
(ii) The path of the particle has different radii on each side of the foil.
The radii are 7.4 cm and 5.7 cm.
Determine the ratio
$$
\frac{\text{final momentum of particle}}{\text{initial momentum of particle}}
$$
for the particle as it passes through the foil.
ratio = ___________________________ [2]
---
© UCLES 2011 9702/41/M/J/11 [Turn over]
For Examiner’s Use
Note: The image pl12 6 A transformer is illustrated in Fig. 6.1. For Examiner's Use  Fig. 6.1 (a) (i) Explain why the coils are wound on a core made of iron. ............................................................................................................................... ............................................................................................................................... [1] (ii) Suggest why thermal energy is generated in the core. ............................................................................................................................... ............................................................................................................................... [2] (b) (i) State Faraday’s law of electromagnetic ind
13 (c) Electrical energy is usually transmitted using alternating current. Suggest why the transmission is achieved using (i) high voltages, ....................................................................................................................... ....................................................................................................................... ....................................................................................................................... [2] (ii) alternating current. ....................................................................................................................... ....................................................................................................................... [1] For Examiner’s U
14 7 Experiments are conducted to investigate the photoelectric effect. (a) It is found that, on exposure of a metal surface to light, either electrons are emitted immediately or they are not emitted at all. Suggest why this observation does not support a wave theory of light. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... [3]
15 (c) Radiation of wavelength 240 nm gives rise to a maximum photoelectric current $I$. The intensity of the incident radiation is maintained constant and the wavelength is now reduced. State and explain the effect of this change on (i) the maximum kinetic energy of the photoelectrons, ............................................................................................................................ ............................................................................................................................ ............................................................................................................................ [2] (ii) the maximum photoelectric current $I$. .............................................................................
16
8 (a) The variation with nucleon number $A$ of the binding energy per nucleon $B_E$ of nuclei is shown in Fig. 8.1.
<div style="text-align: center;">
<br/>
Fig. 8.1
</div>
On Fig. 8.1, mark the approximate positions of
(i) iron-56 (label this point Fe), [1]
(ii) zirconium-97 (label this point Zr), [1]
(iii) hydrogen-2 (label this point H). [1]
(b) (i) State what is meant by *nuclear fission*.
...............................................................................................................................
...............................................................................................................................
.....................................................................................................17 BLANK PAGE Please turn over for Section B. © UCLES 2011 9702/41/M/J/11 [Turn over
18 Section B Answer all the questions in the spaces provided. For Examiner's Use 9 (a) An operational amplifier (op-amp) may be used as a comparator. State the function of a comparator. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... [2] (b) The variation with temperature $\theta$ of the resistance $R$ of a thermistor is shown in Fig. 9.1.  Fig. 9.1 © UCLES 2011 9702/41/M/J/11
19
The thermistor is connected into the circuit of Fig. 9.2.
<div style="text-align: center;">
</div>
Fig. 9.2
The op-amp may be considered to be ideal.
(i) The temperature of the thermistor is $10^\circ \text{C}$ .
Determine the resistance of the variable resistor $X$ such that the output potential $V_{\text{OUT}}$ is zero.
resistance = _________________________ $\Omega$ [2]
(ii) The resistance of the resistor $X$ is now held constant at the value calculated in (i).
Describe the change in the output potential $V_{\text{OUT}}$ as the temperature of the thermistor is changed from $5^\circ \text{C}$ to $20^\circ \text{C}$ .
...............................................................................................................................
.....20
10 (a) State what is meant by the acoustic impedance $Z$ of a medium.
...............................................................................................................................
............................................................................................................................... [1]
(b) Two media have acoustic impedances $Z_1$ and $Z_2$ .
The intensity reflection coefficient $\alpha$ for the boundary between the two media is given by
$$
\alpha = \frac{(Z_2 - Z_1)^2}{(Z_2 + Z_1)^2}.
$$
Describe the effect on the transmission of ultrasound through a boundary where there is a large difference between the acoustic impedances of the two media.
...............................................................................................21
The intensity of the parallel ultrasound beam entering the surface S of the layer of fat is $I$. The beam is reflected from the boundary between fat and muscle. The intensity of the reflected ultrasound detected at the surface S of the fat is $0.012\,I$. Calculate
(i) the intensity reflection coefficient at the boundary between the fat and the muscle,
$$
\text{coefficient} = \underline{\hspace{5cm}} [2]
$$
(ii) the thickness $x$ of the layer of fat.
$$
x = \underline{\hspace{5cm}} \text{ cm } [3]
$$
For Examiner’s Use
© UCLES 2011 9702/41/M/J/11 [Turn over
Note: The document contains a vertical line on the right side labeled "For Examiner’s Use" and a footer with copyright and document identifiers. The mathematical expressions are rendered in LaTeX notation as requested. The bla22
11 (a) Describe what is meant by frequency modulation (FM).
...............................................................................................................................
...............................................................................................................................
............................................................................................................................... [2]
(b) A sinusoidal carrier wave has a frequency of 600 kHz and an amplitude of 5.0 V.
The carrier wave is frequency modulated by a sinusoidal wave of frequency 7.0 kHz and amplitude 2.0 V.
The frequency deviation of the carrier wave is 20 kHz V⁻¹.
Determine, for the modulated carrier wave,
(i) the amplitude,
$\text{amplitude} = \underli23 12 Many television receivers are connected to an aerial using a coaxial cable. Such a cable is illustrated in Fig. 12.1. <div style="text-align: center;">  <br/> Fig. 12.1 </div> (a) State two functions of the copper braid. 1. ....................................................................................................................... 2. ....................................................................................................................... [2] (b) Suggest two reasons why a coaxial cable is used, rather than a wire pair, to connect the aerial to the receiver. 1. ....................................................................................................................... 2. ............................................