9702_w08_qp_4
A paper of Physics, 9702
Questions:
11
Year:
2008
Paper:
4
Variant:
0
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1
A spherical planet has mass M and radius R. The planet may be assumed to be isolated in space and to have its mass concentrated at its centre. The planet spins on its axis with angular speed ω, as illustrated in . R mass m pole of planet equator of planet A small object of mass m rests on the equator of the planet. The surface of the planet exerts a normal reaction force on the mass. State formulae, in terms of M, m, R and ω, for the gravitational force between the planet and the object, the centripetal force required for circular motion of the small mass, the normal reaction exerted by the planet on the mass. Explain why the normal reaction on the mass will have different values at the equator and at the poles. For Examiner’s Use The radius of the planet is 6.4 × 106 m. It completes one revolution in 8.6 × 104 s. Calculate the magnitude of the centripetal acceleration at 1. the equator, acceleration = m s–2 2. one of the poles. acceleration = m s–2 Suggest two factors that could, in the case of a real planet, cause variations in the acceleration of free fall at its surface. 1. 2.
13. Gravitational fields  →  13.2. Gravitational force between point masses
3. Dynamics  →  3.1. Momentum and Newton’s laws of motion
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2
For Examiner’s Use Define specific latent heat of fusion. Some crushed ice at 0 °C is placed in a funnel together with an electric heater, as shown in . ××× crushed ice funnel beaker heater joule- meter supply The mass of water collected in the beaker in a measured interval of time is determined with the heater switched off. The mass is then found with the heater switched on. The energy supplied to the heater is also measured. For both measurements of the mass, water is not collected until melting occurs at a constant rate. The data shown in are obtained. mass of water / g energy supplied to heater / J time interval / min heater switched off heater switched on 16.6 64.7 10.0 5.0 State why the mass of water is determined with the heater switched off. For Examiner’s Use Suggest how it can be determined that the ice is melting at a constant rate. Calculate a value for the specific latent heat of fusion of ice. latent heat = kJ kg–1
14. Temperature  →  14.3. Specific heat capacity and specific latent heat
23. Nuclear physics  →  23.1. Mass defect and nuclear binding energy
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3
For Examiner’s Use The needle of a sewing machine is made to oscillate vertically through a total distance of 22 mm, as shown in . needle at its maximum height 22 mm 8.0 mm cloth The oscillations are simple harmonic with a frequency of 4.5 Hz. The cloth that is being sewn is positioned 8.0 mm below the point of the needle when the needle is at its maximum height. State what is meant by simple harmonic motion. The displacement y of the point of the needle may be represented by the equation y = a cosω t. Suggest the position of the point of the needle at time t = 0. Determine the values of 1. a, a = mm 2. ω. ω = rad s–1 For Examiner’s Use Calculate, for the point of the needle, its maximum speed, speed = m s–1 its speed as it moves downwards through the cloth. speed = m s–1
17. Oscillations  →  17.1. Simple harmonic oscillations
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5
For Examiner’s Use Two deuterium (2 1H) nuclei are travelling directly towards one another. When their separation is large compared with their diameters, they each have speed v as illustrated in . v v deuterium nucleus deuterium nucleus The diameter of a deuterium nucleus is 1.1 × 10–14 m. Use energy considerations to show that the initial speed v of the deuterium nuclei must be approximately 2.5 × 106 m s–1 in order that they may come into contact. Explain your working. For a fusion reaction to occur, the deuterium nuclei must come into contact. Assuming that deuterium behaves as an ideal gas, deduce a value for the temperature of the deuterium such that the nuclei have an r.m.s. speed equal to the speed calculated in . temperature = K Comment on your answer to .
23. Nuclear physics  →  23.1. Mass defect and nuclear binding energy
11. Particle physics  →  11.1. Atoms, nuclei and radiation
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6
For Examiner’s Use A simple iron-cored transformer is illustrated in . laminated soft-iron core secondary coil primary coil Suggest why the core is a continuous loop, laminated. State Faraday’s law of electromagnetic induction. Use Faraday’s law to explain the operation of the transformer. For Examiner’s Use State two advantages of the use of alternating voltages for the transmission and use of electrical energy. 1. 2.
20. Magnetic fields  →  20.5. Electromagnetic induction
20. Magnetic fields  →  20.4. Magnetic fields due to currents
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7
For Examiner’s Use State three pieces of evidence provided by the photoelectric effect for a particulate nature of electromagnetic radiation. 1. 2. 3. Briefly describe the concept of a photon. Explain how lines in the emission spectrum of gases at low pressure provide evidence for discrete electron energy levels in atoms. For Examiner’s Use Three electron energy levels in atomic hydrogen are represented in . increasing energy The wavelengths of the spectral lines produced by electron transitions between these three energy levels are 486 nm, 656 nm and 1880 nm. On , draw arrows to show the electron transitions between the energy levels that would give rise to these wavelengths. Label each arrow with the wavelength of the emitted photon. Calculate the maximum change in energy of an electron when making transitions between these levels. energy = J
22. Quantum physics  →  22.4. Energy levels in atoms and line spectra
22. Quantum physics  →  22.2. Photoelectric effect
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8
For Examiner’s Use Describe what is meant by a magnetic field. A small mass is placed in a field of force that is either electric or magnetic or gravitational. State the nature of the field of force when the mass is charged and the force is opposite to the direction of the field, uncharged and the force is in the direction of the field, charged and there is a force only when the mass is moving, charged and there is no force on the mass when it is stationary or moving in a particular direction.
20. Magnetic fields  →  20.3. Force on a moving charge
20. Magnetic fields  →  20.1. Concept of a magnetic field
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10
For Examiner’s Use 10 The circuit for an amplifier incorporating an ideal operational amplifier (op-amp) is shown in . – + +9 V P R2 –9 V R1 VIN VOUT State 1. the name of this type of amplifier circuit, 2. why the point P is referred to as a virtual earth. Show that the gain G of this amplifier circuit is given by the expression G = – R2 ––– R1 . Explain your working. For Examiner’s Use The circuit of is modified by connecting a light-dependent resistor (LDR) as shown in . – + +9 V R2 –9 V R1 VIN VOUT = +1.2 V V The resistances R1 and R2 are 5.0 kΩ and 50 kΩ respectively. The input voltage VIN is +1.2 V. A high-resistance voltmeter measures the output VOUT. The circuit is used to monitor low light intensities. Determine the voltmeter reading for light intensities such that the LDR has a resistance of 1. 100 kΩ, reading = V 2. 10 kΩ. reading = V For Examiner’s Use The light incident on the LDR is provided by a single lamp. Use your answers in to describe and explain qualitatively the variation of the voltmeter reading as the lamp is moved away from the LDR.
9. Electricity  →  9.3. Resistance and resistivity
10. D.C. circuits  →  10.3. Potential dividers
10. D.C. circuits  →  10.1. Practical circuits
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