2020 Physics 9702 Paper 11

2020 Physics 9702 Paper 11 (pdf)

• Solutions

1. Which quantity is a physical quantity?
   A atomic number
   B efficiency
   C number density of charge carriers
   D strain
   
2. Which time interval is the shortest?
   A 0.05 ms B 50 ns C 500 000 ps D 0.5 μs
   
3. P and R are coplanar vectors.
   If X = P – R, which diagram best represents vector X?
   
4. A student uses a cathode-ray oscilloscope (CRO) to measure the period of a signal. She sets the time-base of the CRO to 5 ms cm^–1 and observes the trace illustrated below. The trace has a length of 10.0 cm.
   What is the period of the signal?
   
5. The diameter of a spherical golf ball is measured with calipers and found to be (4.11 ± 0.01) cm.
   The volume of a sphere is V = 1/6 πd³, where d is the diameter of the sphere.
   What is the volume of the golf ball?

6. A student cycles uphill from home to a shop, taking 10 minutes. The student then spends 5 minutes in the shop, before cycling home downhill at twice the initial speed.
   Which graph could show the variation with time of the distance travelled by the cyclist?
   
7. Two cars X and Y are travelling along the same straight road. Car X is travelling at a constant speed of 6.0 m s^–1. Car Y has a constant acceleration of 0.50 m s^–2.
   At the instant shown, car X is a distance d ahead of car Y. Car Y is travelling at a speed of 4.0 m s^–1.
   Car Y is level with car X after a time of 20 seconds.
   What is the distance d?
   
8. The graph shows how quantity P varies with quantity Q for an object falling in air for a long time in a uniform gravitational field.
   What could be the identities of P and Q?
   
9. A rock R of mass 1.0 × 10²⁷ kg is a large distance from a star S and is travelling at a speed of 1.0 × 10⁴ m s^-1. The star has mass 1.0 7times; 10³⁰ kg. The rock travels around the star on the path shown so that it reverses its direction of motion and, when finally again a large distance from the star, has the same speed as initially.
   
10. The diagram shows the masses and velocities of two trolleys that are about to collide.
    After the impact they move off together.
    What is the kinetic energy lost in the collision?
    
11. A particle is situated at rest between two metal plates X and Y.
    A potential difference (p.d.) is then applied across the plates and produces the electric field shown.
    The particle moves towards plate X when the p.d. is applied.
    What could be the particle?
    
12. Two people push a vertical gate to open it. The forces exerted by the people on the gate are shown.
    One person is distance d₁ from the gate’s hinge and pushes with horizontal force F₁ at angle θ₁ to the gate.
    The other person is at distance d₂ from the hinge and pushes with horizontal force F₂ at an angle θ₂ to the gate.
    What is the total moment about the hinge due to forces F1 and F2?
    
13. A ball is rolling down a slope at a constant speed. The three forces acting on the ball are its weight, the contact force normal to the slope and friction.
    Which diagram could represent these three forces?
    
14. One end of a U-shaped tube is attached to a gas tap, with its other end open to the atmosphere.
    It contains water of density 1000 kg m^–3 and the heights of both sides of the water column are shown The atmospheric pressure is 101 kPa.
    What is the pressure of the gas from the gas tap?
    
15. A trolley runs from P to Q along a track. At Q its potential energy is 50 kJ less than at P. At P, the kinetic energy of the trolley is 5 kJ. Between P and Q, the trolley does 10 kJ of work against friction.
    What is the kinetic energy of the trolley at Q?
    
16. A hydroelectric power station uses the gravitational potential energy of water to generate electrical energy.
    In one particular power station, the mass of water flowing per unit time is 1.5 × 105 kgs^–1. The water falls through a vertical height of 120 m.
    The electrical power generated is 100 MW.
    What is the efficiency of the power station?
    
17. Which amount of energy is not 2400 J?
    
18. A train of mass 300 000kg is accelerating at 0.80 m s^–2. At one instant, the speed of the train is 5.0 m s^–1 and the resistive force to its motion is 15 kN.
    At this instant, what is the rate of increase of kinetic energy of the train?
    
19. A wire of circular cross-section, which obeys Hooke’s law, is used to suspend a basket as shown The Young modulus for the material of the wire is 2.5 × 10¹¹Pa.
    When a weight of 34 N is added to the basket, the strain in the wire increases by 6.0 × 10^–5.
    What is the radius of the wire?
    
20. An unstretched rubber cord is stretched by a force. The force F is plotted against the extension x. F is slowly increased from zero, causing the cord to extend along path P. F is then reduced back to zero along path Q
    
21. A guitar string vibrates to create a sound. The speed of the wave in the guitar string is always 440 m s^–1. The vibrating string creates a sound wave that moves in the air with a speed of 330 m s^–1.
    Which graph shows the variation of frequency f with the wavelength  for the waves in the string and in the air?
    
22. The graph shows the variation with time of displacement for two different waves X and Y Wave X has frequency f and amplitude A.
    What is the frequency and what is the amplitude of wave Y?
    
23. A loudspeaker emits a sound wave into a tube initially full of water
    A tap at the bottom of the tube is opened so that water slowly leaves the tube. For some lengths of the air column in the tube, the sound heard is much louder.
    The first loud sound is heard when the air column in the tube has length x.
    The next time that a loud sound is heard is when the air column in the tube has length y.
    What is the wavelength of the sound wave from the loudspeaker?
    
24. A source of sound of frequency 1000 Hz directly approaches a stationary observer. The observer measures the frequency of the received sound to be 1500 Hz. The speed of sound in still air is 330 m s^–1.
    What is the speed of the source of sound?
    
25. The graph shows how the intensity of electromagnetic radiation emitted from a distant star varies with wavelength
    In which region of the electromagnetic spectrum is the radiation of greatest intensity?
    
26. Which statement concerning a stationary wave is correct?
    
27. Which waves would best demonstrate diffraction through a doorway?
    
28. Two loudspeakers are placed near to each other and facing in the same direction.
    A microphone connected to an oscilloscope is moved along a line some distance away from the loudspeakers, as shown.
    Which statement about the waves emitted by the loudspeakers is not a necessary condition for the microphone to detect a fixed point along the line where there is no sound?
    
29. A parallel beam of white light passes through a diffraction grating. Orange light of wavelength 600 nm in the fourth-order diffraction maximum coincides with blue light in the fifth-order diffraction maximum.
    What is the wavelength of the blue light?
    
30. The diagram shows the electric field near a positively charged sphere and a negatively charged sphere.
    Four electrons A, B, C and D are shown at different positions in the field.
    On which electron is the direction of the force on the electron shown correctly?
    
31. An oil drop has mass m and charge q. The drop is held stationary in an electric field between two parallel horizontal plates, a distance d apart, as shown.
    The potential difference between the plates is V and the acceleration of free fall is g.
    What is the charge-to-mass ratio q/m of the oil drop?
    
32. Free electrons flow along a copper wire X of radius 5.0 × 10^–5 m with an average drift speed of 2.8 × 10^–2 m s^–1. The current in the wire is 3.0A.
    There is a current of 2.0A in a copper wire Y of radius 1.0 × 10^–4 m.
    What is the average drift speed of the free electrons in copper wire Y?
    
33. What is the definition of potential difference?
    
34. A cable of length L consisting of two wires is used to connect a 12.0V power supply of negligible internal resistance to a lamp, as shown.
    The potential difference across the lamp is 10.5V. The current in the wire is 2.50A.
    Each wire is made of metal of resistivity 1.70 × 10^–8Ω m and has a cross-sectional area of 6.00 × 10^–7m².
    What is the length L of the cable?
    
35. In the circuits shown, the power supply has an electromotive force (e.m.f.) greater than the normal operating voltage of the lamp. The internal resistance of the power supply is negligible.
    The resistance of the variable resistor is adjusted from zero to its maximum value.
    In which circuit could the voltage across the lamp change from zero to its normal operating voltage and not exceed its normal operating voltage?
    
36. Three identical lamps L1, L2 and L3 are connected to a battery with negligible internal resistance, as shown.
    What happens to the brightness of lamps L1 and L2 when the switch S is closed?
    
37. In the circuit shown, the 6.0V battery has negligible internal resistance. Resistors R1 and R2 and the voltmeter each have a resistance of 100 kΩ.
    What is the current in the resistor R2?
    
38. Which statement about two nuclei that are isotopes of the same element is correct?
    
39. In a nuclear physics experiment
40. Which diagram represents the quark composition of an antineutron?

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