科目：物理 Physics (9702)
年份：2010 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
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Section A
Answer all the questions in the spaces provided.
For Examiner's Use
1 A planet of mass $m$ is in a circular orbit of radius $r$ about the Sun of mass $M$ , as illustrated in Fig. 1.1.
<div style="text-align: center;">
</div>
Fig. 1.1
The magnitude of the angular velocity and the period of revolution of the planet about the Sun are $\omega$ and $T$ respectively.
(a) State
(i) what is meant by *angular velocity*,
...............................................................................................................................
...............................................................................................................................
...............................................................................5
(c) Data for the planets Venus and Neptune are given in Fig. 1.2.
<table>
<tr>
<th>planet</th>
<th>$r / 10^8$ km</th>
<th>$T$ / years</th>
</tr>
<tr>
<td>Venus</td>
<td>1.08</td>
<td>0.615</td>
</tr>
<tr>
<td>Neptune</td>
<td>45.0</td>
<td></td>
</tr>
</table>
Fig. 1.2
Assume that the orbits of both planets are circular.
(i) Use the expression in (b) to calculate the value of $T$ for Neptune.
$$
T = \underline{\hspace{5cm}} \text{ years [2]}
$$
(ii) Determine the linear speed of Venus in its orbit.
$$
\text{speed} = \underline{\hspace{5cm}} \text{ km s}^{-1} \text{ [2]}
$$
For Examiner's Use
© UCLES 2010 9702/43/O/N/10 [Turn over6 2 (a) State the basic assumptions of the kinetic theory of gases. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... [4] (b) Use equations for the pressure of an ideal gas to deduce that the average tra
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(ii) For the reaction to occur, the minimum total kinetic energy of the deuterium nucleus and the proton is $2.4 \times 10^{-14}$ J. Assuming that a sample of a mixture of deuterium nuclei and protons behaves as an ideal gas, calculate the temperature of the sample for this reaction to occur.
temperature = ………………………………………… K [3]
(iii) Suggest why the assumption made in (ii) may not be valid.
………………………………………………………………………………………………………
………………………………………………………………………………………………………[1]
For Examiner’s Use
© UCLES 2010 9702/43/O/N/10 [Turn over8
3 A cylinder and piston, used in a car engine, are illustrated in Fig. 3.1.
<div style="text-align: center;">
</div>
Fig. 3.1
The vertical motion of the piston in the cylinder is assumed to be simple harmonic.
The top surface of the piston is at AB when it is at its lowest position; it is at CD when at its highest position, as marked in Fig. 3.1.
(a) The displacement $d$ of the piston may be represented by the equation
$$
d = -4.0 \cos(220t)
$$
where $d$ is measured in centimetres.
(i) State the distance between the lowest position AB and the highest position CD of the top surface of the piston.
distance = …………………………… cm [1]
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© UCLES 2010 9702/43/O/N/10
For Examiner’s Use9 (ii) Determine the number of oscillations made per second by the piston. number = ………………………………………… [2] (iii) On Fig. 3.1, draw a line to represent the top surface of the piston in the position where the speed of the piston is maximum. [1] (iv) Calculate the maximum speed of the piston. speed = ………………………………………… cm s⁻¹ [2] For Examiner’s Use © UCLES 2010 9702/43/O/N/10 [Turn over
10 (b) The engine of a car has several cylinders. Three of these cylinders are shown in Fig. 3.2. <div style="display: flex; justify-content: space-between; width: 100%;"> <div style="text-align: center;"> X<br>  </div> <div style="text-align: center;"> Y<br>  </div> <div style="text-align: center;"> Z<br>  </div> </div> Fig. 3.2 X is the same cylinder and piston as in Fig. 3.1. Y and Z are two further cylinders, with the lowest and the highest positions of the top surface of each piston indicated. The pistons in the cylinders each have the same frequency of oscillation, but they are not in phase. At a particular instant in time, the position of the top of the piston in cylinder X is as shown. (i) In cylinder Y, the
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(ii) In cylinder Z, the oscillations of the piston lead those of the piston in cylinder X by a phase angle of $240^\circ$ ( $\frac{4}{3}\pi$ rad).
Complete the diagram of cylinder Z, for this instant, by drawing
1. a line to show the top surface of the piston, [1]
2. an arrow to show the direction of movement of the piston. [1]
(iii) For the piston in cylinder Y, calculate its speed for this instant.
speed = …………………………… cm s $^{-1}$ [2]
For Examiner’s Use
© UCLES 2010 9702/43/O/N/10 [Turn over12 4 (a) (i) State what is meant by *electric potential* at a point. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... [2] (ii) Define *capacitance*. ............................................................................................................................... ............................................................................................................................... [1] (b) The variation of the potential $V$ of an iso
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An isolated metal sphere has capacitance.
Use Fig. 4.1 to determine
(i) the capacitance of the sphere,
$$
\text{capacitance} = \underline{\hspace{5cm}} \text{ F [2]}
$$
(ii) the electric potential energy stored on the sphere when charged to a potential of 150 kV.
$$
\text{energy} = \underline{\hspace{5cm}} \text{ J [2]}
$$
(c) A spark reduces the potential of the sphere from 150 kV to 75 kV.
Calculate the energy lost from the sphere.
$$
\text{energy} = \underline{\hspace{5cm}} \text{ J [2]}
$$
For Examiner’s Use
© UCLES 2010 9702/43/O/N/10 [Turn over14
5 The poles of a horseshoe magnet measure $5.0 \text{ cm} \times 2.4 \text{ cm}$ , as shown in Fig. 5.1.
<div style="text-align: center;">
</div>
Fig. 5.1
The uniform magnetic flux density between the poles of the magnet is $89 \text{ mT}$ . Outside the region of the poles, the magnetic flux density is zero.
A stiff copper wire is connected to a sensitive ammeter of resistance $0.12 \Omega$ . A student moves the wire at a constant speed of $1.8 \text{ m s}^{-1}$ between the poles in a direction parallel to the faces of the poles.
(a) Calculate the magnetic flux between the poles of the magnet.
$$
\text{magnetic flux} = \underline{\hspace{5cm}} \text{ Wb [2]}
$$
(b) (i) Use your answer in (a) to determine, for the wire moving between the poles of the mag15 (ii) Show that the reading on the ammeter is approximately 70 mA. For Examiner's Use [1] (c) By reference to Lenz’s law, a force acts on the wire to oppose the motion of the wire. The student who moved the wire between the poles of the magnet claims not to have felt this force. Explain quantitatively a reason for this claim. ............................................................................................................................... ............................................................................................................................... [3] © UCLES 2010 9702/43/O/N/10 [Turn over]
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6 The variation with time $t$ of the current $I$ in a resistor is shown in Fig. 6.1.
<div style="text-align: center;">
</div>
Fig. 6.1
The variation of the current with time is sinusoidal.
(a) Explain why, although the current is not in one direction only, power is converted in the resistor.
...............................................................................................................................
...............................................................................................................................
............................................................................................................................... [2]
(b) Using the relation between root-mean-square (r.m.s.) current and peak current17
7 Electrons are moving through a vacuum in a narrow beam. The electrons have speed $v$ . The electrons enter a region of uniform magnetic field of flux density $B$ . Initially, the electrons are travelling at a right-angle to the magnetic field. The path of a single electron is shown in Fig. 7.1.
<div style="text-align: center;">
</div>
Fig. 7.1
The electrons follow a curved path in the magnetic field.
A uniform electric field of field strength $E$ is now applied in the same region as the magnetic field. The electrons pass undeviated through the region of the two fields. Gravitational effects may be neglected.
(a) Derive a relation between $v$ , $E$ and $B$ for the electrons not to be deflected. Explain your working.
.....................................18
8 (a) By reference to the photoelectric effect, state what is meant by the *threshold frequency*.
...............................................................................................................................
...............................................................................................................................
............................................................................................................................... [2]
(b) The surface of a zinc plate has a work function of $5.8 \times 10^{-19} \text{J}$ .
In a particular laboratory experiment, ultraviolet light of wavelength 120 nm is incident on the zinc plate. A photoelectric current $I$ is detected.
In order to view the apparatus more clearly, a second lamp emittin19 Section B Answer all the questions in the spaces provided. For Examiner's Use 9 (a) (i) State, with reference to X-ray images, what is meant by sharpness. ............................................................................................................................... ............................................................................................................................... [1] (ii) Describe briefly two factors that affect the sharpness of an X-ray image. 1. ............................................................................................................................... ............................................................................................................................... 2. ...............................
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10 (a) State three properties of an ideal operational amplifier (op-amp).
1. .......................................................................................................................
2. .......................................................................................................................
3. .......................................................................................................................
[3]
(b) A circuit incorporating an ideal op-amp is to be used to indicate whether a door is open or closed.
Resistors, each of resistance $R$, are connected to the inputs of the op-amp, as shown in Fig. 10.1.
+3 V
|
S / R R
| | |
| | |
| | |
| | |
| | |
| 21 (i) Explain why the polarity of the output of the op-amp changes when the switch closes. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... [3] (ii) A red light-emitting diode (LED) is to be used to indicate when the door is open. A green LED is to indicate when the door is closed. On Fig. 10.1, 1. draw symbols for the LEDs
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11 The linear attenuation (absorption) coefficient $\mu$ for X-ray radiation in bone, fat and muscle is given in Fig. 11.1.
<table>
<tr>
<td></td>
<td> $\mu / \text{cm}^{-1}$ </td>
</tr>
<tr>
<td>bone</td>
<td>2.9</td>
</tr>
<tr>
<td>fat</td>
<td>0.90</td>
</tr>
<tr>
<td>muscle</td>
<td>0.95</td>
</tr>
</table>
Fig. 11.1
(a) A parallel X-ray beam of intensity $I_0$ is incident either on some bone or on some muscle.
The emergent beam has intensity $I$ .
Calculate the ratio $\frac{I}{I_0}$ for a thickness of
(i) 1.5 cm of bone,
ratio = ………………………………………… [2]
(ii) 4.6 cm of muscle.
ratio = ………………………………………… [1]
(b) Suggest why, on an X-ray plate, the contrast between bone and muscle is much greater than that between fat a23 12 (a) Data may be transmitted as an analogue signal or as a digital signal. (i) Explain what is meant by 1. an *analogue* signal, ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... 2. a *digital* signal. ............................................................................................................................... ..........................................................................................................................