9702_s15_qp_42
A paper of Physics, 9702
Questions:
12
Year:
2015
Paper:
4
Variant:
2
Login to start this paper & get access to powerful tools
1
The Earth may be considered to be a uniform sphere of radius 6.37 × 103 km with its mass of 5.98 × 1024 kg concentrated at its centre. The Earth spins on its axis with a period of 24.0 hours. A stone of mass 2.50 kg rests on the Earth’s surface at the Equator. 1. Calculate, using Newton’s law of gravitation, the gravitational force on the stone. gravitational force = N 2. Determine the force required to maintain the stone in its circular path. force = N The stone is now hung from a newton-meter. Use your answers in to determine the reading on the meter. Give your answer to three significant figures. reading = N A satellite is orbiting the Earth. For an astronaut in the satellite, his sensation of weight is caused by the contact force from his surroundings. The astronaut reports that he is ‘weightless’, despite being in the Earth’s gravitational field. Suggest what is meant by the astronaut reporting that he is ‘weightless’.
13. Gravitational fields  →  13.2. Gravitational force between point masses
3. Dynamics  →  3.1. Momentum and Newton’s laws of motion
Open
3
Define specific latent heat. A beaker containing a liquid is placed on a balance, as shown in . liquid insulation heater pan of balance A heater of power 110 W is immersed in the liquid. The heater is switched on and, when the liquid is boiling, balance readings m are taken at corresponding times t. A graph of the variation with time t of the balance reading m is shown in . m / g t / min State the feature of which suggests that the liquid is boiling at a steady rate. Use data from to determine a value for the specific latent heat L of vaporisation of the liquid. L = J kg–1 State, with a reason, whether the value determined in is likely to be an overestimate or an underestimate of the normally accepted value for the specific latent heat of vaporisation of the liquid.
14. Temperature  →  14.3. Specific heat capacity and specific latent heat
14. Temperature  →  14.2. Temperature scales
Open
4
State what is meant by simple harmonic motion. The variation with time t of the displacement x of two oscillators P and Q is shown in . x / cm −4 −2 −1 −3 2.8 2.4 2.0 1.6 1.2 0.8 0.4 t / s oscillator P oscillator Q The two oscillators each have the same mass. Use to determine the phase difference between the two oscillators, phase difference = rad the maximum acceleration of oscillator Q, maximum acceleration = m s–2 the ratio maximum kinetic energy of oscillations of Q maximum kinetic energy of oscillations of P . ratio = Use data from to sketch, on the axes of , the variation with displacement x of the acceleration a of oscillator Q. –3 –2 –1 a –4 x / cm
17. Oscillations  →  17.1. Simple harmonic oscillations
Open
5
Define electric potential at a point. Two positively charged metal spheres A and B are situated in a vacuum, as shown in . sphere A P x sphere B A point P lies on the line joining the centres of the two spheres and is a distance x from the surface of sphere A. The variation with x of the electric potential V due to the two charged spheres is shown in . surface of A surface of B V / V x / cm State how the magnitude of the electric field strength at any point P may be determined from the graph of . Without any calculation, describe the force acting on a positively charged particle placed at point P for values of x from x = 0 to x = 10 cm. The positively charged particle in has charge q and mass m given by the expression q m = 4.8 × 107 C kg–1. Initially, the particle is at rest on the surface of sphere A where x = 0. It then moves freely along the line joining the centres of the spheres until it reaches the surface of sphere B. On , mark with the letter M the point where the charged particle has its maximum speed. 1. Use to determine the potential difference between the spheres. potential difference = V 2. Use your answer in part 1 to calculate the speed of the particle as it reaches the surface of sphere B. Explain your working. speed = m s–1
18. Electric fields  →  18.5. Electric potential
18. Electric fields  →  18.3. Electric force between point charges
Open
6
Explain what is meant by a photon. An X-ray photon of energy 3.06 × 10–14 J is incident on an isolated stationary electron, as illustrated in . incident photon deflected photon wavelength 6.80 × 10–12 m e energy 3.06 × 10–14 J The photon is deflected elastically by the electron through angle θ. The deflected photon has a wavelength of 6.80 × 10–12 m. On , draw an arrow to indicate a possible initial direction of motion of the electron after the photon has been deflected. Calculate 1. the energy of the deflected photon, photon energy = J 2. the speed of the electron after the photon has been deflected. speed = m s–1 Explain why the magnitude of the final momentum of the electron is not equal to the change in magnitude of the momentum of the photon.
22. Quantum physics  →  22.1. Energy and momentum of a photon
Open
7
A solenoid is connected in series with a resistor, as shown in . N S motion of magnet As the magnet is being moved into the solenoid, thermal energy is transferred in the resistor. Use laws of electromagnetic induction to explain the origin of this thermal energy. Explain why the alternating current in the primary coil of a transformer is not in phase with the alternating e.m.f. induced in the secondary coil.
20. Magnetic fields  →  20.4. Magnetic fields due to currents
20. Magnetic fields  →  20.5. Electromagnetic induction
Open
8
The power for a space probe is to be supplied by the energy released when plutonium-236 decays by the emission of α-particles. The α-particles, each of energy 5.75 MeV, are captured and their energy is converted into electrical energy with an efficiency of 24%. Calculate the energy, in joules, equal to 5.75 MeV, energy = J the number of α-particles per second required to generate 1.9 kW of electrical power. number per second = s–1 Each plutonium-236 nucleus, on disintegration, produces one α-particle. Plutonium-236 has a half-life of 2.8 years. Calculate the decay constant, in s–1, of plutonium-236. decay constant = s–1 Use your answers in and to determine the mass of plutonium-236 required for the generation of 1.9 kW of electrical power. mass = g The minimum electrical power required for the space probe is 0.84 kW. Calculate the time, in years, for which the sample of plutonium-236 in will provide sufficient power. time = years
23. Nuclear physics  →  23.1. Mass defect and nuclear binding energy
23. Nuclear physics  →  23.2. Radioactive decay
Open
9
The strain in a beam is to be monitored using a strain gauge. The strain gauge is included in the potential divider circuit shown in . strain gauge 120.0 1 +2000 mV 5000 1 5000 1 B A The strain gauge has a resistance of 120.0 Ω when it is not strained. The resistance increases to 121.5 Ω when the strain is ε. Calculate the potential difference between points A and B on when the strain in the gauge is ε. potential difference = mV An inverting amplifier, incorporating an operational amplifier (op-amp), uses a high-resistance voltmeter to display the output. A partially completed circuit for the amplifier is shown in . V IN +9 V –9 V V + – The voltmeter is to indicate a full-scale deflection of +6.0 V for an input potential VIN of 0.15 V. On , 1. complete the circuit for the inverting amplifier, 2. mark, with the letter P, the positive terminal of the voltmeter. Suggest appropriate values for the resistors you have shown in . Label the resistors in with these values.
6. Deformation of solids  →  6.1. Stress and strain
Open
10
State what is meant by the specific acoustic impedance of a medium. The specific acoustic impedances Z of some media are given in . Z / kg m–2 s–1 air gel soft tissue bone 4.3 × 102 1.5 × 106 1.6 × 106 7.0 × 106 The density of a sample of bone is 1.7 × 103 kg m–3. Determine the wavelength, in mm, of ultrasound of frequency 9.0 × 105 Hz in the bone. wavelength = mm Ultrasound of intensity I is incident normally on the boundary between two media of specific acoustic impedances Z1 and Z2, as shown in . incident intensity I Z 1 Z 2 reflected intensity IR The intensity of the ultrasound reflected from the boundary is IR. The ratio IR I is given by the expression IR I = (Z1 – Z2)2 (Z1 + Z2)2 . By making reference to the data for air, gel and soft tissue, explain quantitatively why, during medical diagnosis using ultrasound, a gel is usually put on the skin.
24. Medical physics  →  24.1. Production and use of ultrasound
Open
11
One channel of communication is by the use of a coaxial cable. Such a cable is illustrated in . A inner copper wire plastic insulation protective covering Suggest the material from which the component labelled A on is made. Suggest two functions of the component labelled A. 1. 2. When a signal travels along the coaxial cable, it is attenuated. State the meaning of attenuation. State and explain why attenuation is frequently measured in decibels (dB). A television aerial is connected to a receiver using a coaxial cable of length 11 m. The attenuation per unit length of the cable is 190 dB km–1. Calculate the ratio output signal from coaxial cable input signal to coaxial cable . ratio = Please turn over for Question 12.
24. Medical physics  →  24.1. Production and use of ultrasound
24. Medical physics  →  24.2. Production and use of X-rays
Open