9702_w12_qp_42
A paper of Physics, 9702
Questions:
12
Year:
2012
Paper:
4
Variant:
2
Login to start this paper & get access to powerful tools
1
State Newton’s law of gravitation. A satellite of mass m is in a circular orbit of radius r about a planet of mass M. For this planet, the product GM is 4.00 × 1014 N m2 kg–1, where G is the gravitational constant. The planet may be assumed to be isolated in space. By considering the gravitational force on the satellite and the centripetal force, show that the kinetic energy EK of the satellite is given by the expression EK = GMm 2r . The satellite has mass 620 kg and is initially in a circular orbit of radius 7.34 × 106 m, as illustrated in . 7.34 × 106 m initial orbit new orbit 7.30 × 106 m (not to scale) For Examiner’s Use Resistive forces cause the satellite to move into a new orbit of radius 7.30 × 106 m. Determine, for the satellite, the change in 1. kinetic energy, change in kinetic energy = J 2. gravitational potential energy. change in potential energy = J Use your answers in to explain whether the linear speed of the satellite increases, decreases or remains unchanged when the radius of the orbit decreases.
5. Work, energy and power  →  5.2. Gravitational potential energy and kinetic energy
13. Gravitational fields  →  13.2. Gravitational force between point masses
Open
2
For Examiner’s Use A student suggests that, when an ideal gas is heated from 100 °C to 200 °C, the internal energy of the gas is doubled. State what is meant by internal energy. By reference to one of the assumptions of the kinetic theory of gases and your answer in , deduce what is meant by the internal energy of an ideal gas. State and explain whether the student’s suggestion is correct.
16. Thermodynamics  →  16.1. Internal energy
15. Ideal gases  →  15.3. Kinetic theory of gases
Open
3
For Examiner’s Use Two metal spheres are in thermal equilibrium. State and explain what is meant by thermal equilibrium. An electric water heater contains a tube through which water flows at a constant rate. The water in the tube passes over a heating coil, as shown in . heating coil water out water in tube The water flows into the tube at a temperature of 18 °C. When the power of the heater is 3.8 kW, the temperature of the water at the outlet is 42 °C. The specific heat capacity of water is 4.2 J g–1 K–1. Use the data to calculate the flow rate, in g s–1, of water through the tube. flow rate = g s–1 State and explain whether your answer in is likely to be an overestimate or an underestimate of the flow rate.
14. Temperature  →  14.1. Thermal equilibrium
14. Temperature  →  14.3. Specific heat capacity and specific latent heat
Open
4
For Examiner’s Use A ball is held between two fixed points A and B by means of two stretched springs, as shown in . ball A B The ball is free to oscillate horizontally along the line AB. During the oscillations, the springs remain stretched and do not exceed their limits of proportionality. The variation of the acceleration a of the ball with its displacement x from its equilibrium position is shown in . –3 –5 –10 –15 –2 –1 x / cm a / m s–2 For Examiner’s Use State and explain the features of that indicate that the motion of the ball is simple harmonic. Use to determine, for the oscillations of the ball, the amplitude, amplitude = cm the frequency. frequency = Hz The arrangement in is now rotated through 90° so that the line AB is vertical. The ball now oscillates in a vertical plane. Suggest one reason why the oscillations may no longer be simple harmonic.
17. Oscillations  →  17.1. Simple harmonic oscillations
Open
5
For Examiner’s Use Define capacitance. A capacitor is made of two metal plates, insulated from one another, as shown in . metal plate insulation Explain why the capacitor is said to store energy but not charge. Three uncharged capacitors X, Y and Z, each of capacitance 12 μF, are connected as shown in . 12 ȝF 12 ȝF Z Y 12 ȝF X A B A potential difference of 9.0 V is applied between points A and B. For Examiner’s Use Calculate the combined capacitance of the capacitors X, Y and Z. capacitance = μF Explain why, when the potential difference of 9.0 V is applied, the charge on one plate of capacitor X is 72 μC. Determine 1. the potential difference across capacitor X, potential difference = V 2. the charge on one plate of capacitor Y. charge = μC
19. Capacitance  →  19.1. Capacitors and capacitance
19. Capacitance  →  19.2. Energy stored in a capacitor
Open
6
For Examiner’s Use State the condition for a charged particle to experience a force in a magnetic field. State an expression for the magnetic force F acting on a charged particle in a magnetic field of flux density B. Explain any other symbols you use. A sample of a conductor with rectangular faces is situated in a magnetic field, as shown in . A B direction of magnetic field direction of movement of electrons C G E H D F The magnetic field is normal to face ABCD in the downward direction. Electrons enter face CDHG at right-angles to the face. As the electrons pass through the conductor, they experience a force due to the magnetic field. On , shade the face to which the electrons tend to move as a result of this force. The movement of the electrons in the magnetic field causes a potential difference between two faces of the conductor. Using the lettering from , state the faces between which this potential difference will occur. face and face Explain why the potential difference in causes an additional force on the moving electrons in the conductor.
20. Magnetic fields  →  20.3. Force on a moving charge
20. Magnetic fields  →  20.4. Magnetic fields due to currents
Open
8
For Examiner’s Use State what is meant by a photon. It has been observed that, where photoelectric emission of electrons takes place, there is negligible time delay between illumination of the surface and emission of an electron. State three other pieces of evidence provided by the photoelectric effect for the particulate nature of electromagnetic radiation. 1. 2. 3. The work function of a metal surface is 3.5 eV. Light of wavelength 450 nm is incident on the surface. Determine whether electrons will be emitted, by the photoelectric effect, from the surface.
22. Quantum physics  →  22.2. Photoelectric effect
Open
9
An operational amplifier (op-amp) may be used as part of the processing unit in an electronic sensor. State three properties of an ideal op-amp. 1. 2. 3. A comparator circuit incorporating an ideal op-amp is shown in . – + –5 V +5 V V2 VOUT V1 In one application of the comparator, V2 is kept constant at +1.5 V. The variation with time t of the potential V1 is shown in . The potential V2 is also shown. For Examiner’s Use –2 –4 –6 –8 –10 potential / V V1 t V2 On , show the variation with time t of the output potential VOUT . Two light-emitting diodes (LEDs) R and G are connected to the output of the op-amp in such that R emits light for a longer time than G. On , draw the symbols for the two diodes connected to the output of the op-amp and label the diodes R and G.
10. D.C. circuits  →  10.1. Practical circuits
10. D.C. circuits  →  10.3. Potential dividers
Open
11
For Examiner’s Use 11 In modern communications systems, the majority of data is transmitted in digital form rather than analogue form. Suggest three advantages of the transmission of data in digital form. 1. 2. 3. A recording is made of some music. For this recording, the music is sampled at a rate of 44.1 kHz and each sample consists of a 16-bit word. Suggest the effect on the quality of the recording of 1. sampling at a high frequency rather than a lower frequency, 2. using a long word length rather than a shorter word length. The recording lasts for a total time of 5 minutes 40 seconds. Calculate the number of bits generated during the recording. number =
8. Superposition  →  8.3. Interference
24. Medical physics  →  24.1. Production and use of ultrasound
Open
12
For Examiner’s Use 12 Wire pairs used for the transmission of telephone signals are subject to cross-linking. Explain what is meant by cross-linking. Suggest why cross-linking in coaxial cables is much less than in wire pairs. A wire pair has a length of 1.4 km and is connected to a receiver, as illustrated in . 1.4 km receiver input signal power 3.0 × 10–3 W wire pair constant noise power 3.8 × 10–8 W The constant noise power in the wire pair is 3.8 × 10–8 W. For an input signal to the wire pair of 3.0 × 10–3 W, the signal-to-noise ratio at the receiver is 25 dB. Calculate the attenuation per unit length for the wire pair. attenuation per unit length = dB km–1
8. Superposition  →  8.3. Interference
24. Medical physics  →  24.1. Production and use of ultrasound
20. Magnetic fields  →  20.4. Magnetic fields due to currents
Open