page 12 20. A student carries out an experiment to determine the specific heat capacity c of a solid. The relationship used to calculate c is E c m T = Δ The recorded measurements and their percentage uncertainties are shown. energy supplied, E = 5000 J ± 1% mass of solid, m = 0·20 kg ± 2% change in temperature, ∆T = 4·5 °C ± 5% A good estimate of the percentage uncertainty in the calculated value of c is A 8% B 7% C 5% D 3% E 1%. [END OF SECTION 1. NOW ATTEMPT THE QUESTIONS IN SECTION 2 OF YOUR QUESTION AND ANSWER BOOKLET] H FOR OFFICIAL USE Fill in these boxes and read what is printed below. Number of seat Town © Mark Full name of centre Forename(s) Surname Scottish candidate number Date of birth Year Day Month National Qualications 2018 Total marks — 130 SECTION 1 — 20 marks Attempt ALL questions. Instructions for the completion of Section 1 are given on page 02. SECTION 2 — 110 marks Attempt ALL questions. Reference may be made to the Data Sheet on page 02 of the question paper X757/76/02 and to the Relationships Sheet X757/76/11. Care should be taken to give an appropriate number of significant figures in the final answers to calculations. Write your answers clearly in the spaces provided in this booklet. Additional space for answers and rough work is provided at the end of this booklet. If you use this space you must clearly identify the question number you are attempting. Any rough work must be written in this booklet. You should score through your rough work when you have written your final copy. Use blue or black ink. Before leaving the examination room you must give this booklet to the Invigilator; if you do not, you may lose all the marks for this paper. X757/76/01 TUESDAY, 8 MAY 9:00 AM – 11:30 AM A/PB Physics Section 1 — Answer Grid and Section 2 page 02 SECTION 1 — 20 marks The questions for Section 1 are contained in the question paper X757/76/02. Read these and record your answers on the answer grid on page 03 opposite. Use blue or black ink. Do NOT use gel pens or pencil. 1. The answer to each question is either A, B, C, D or E. Decide what your answer is, then fill in the appropriate bubble (see sample question below). 2. There is only one correct answer to each question. 3. Any rough working should be done on the additional space for answers and rough work at the end of this booklet. Sample question The energy unit measured by the electricity meter in your home is the A ampere B kilowatt-hour C watt D coulomb E volt. The correct answer is B — kilowatt-hour. The answer B bubble has been clearly filled in (see below). A B C D E Changing an answer If you decide to change your answer, cancel your first answer by putting a cross through it (see below) and fill in the answer you want. The answer below has been changed to D. A B C D E If you then decide to change back to an answer you have already scored out, put a tick (3) to the right of the answer you want, as shown below: A B C D E or A B C D E page 03 A B C D E 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 SECTION 1 — Answer Grid [Turn over page 04 [BLANK PAGE] DO NOT WRITE ON THIS PAGE page 05 [Turn over for SECTION 2 DO NOT WRITE ON THIS PAGE page 06 MARKS DO NOT WRITE IN THIS MARGIN SECTION 2 — 110 marks Attempt ALL questions 1. During a school funfair, a student throws a wet sponge at a teacher. The sponge is thrown with an initial velocity of 7·4 m s−1 at an angle of 30° to the horizontal. The sponge leaves the student’s hand at a height of 1·5 m above the ground. h 7·4 m s−1 30° 1·5 m not to scale The sponge hits the teacher. The effects of air resistance can be ignored. (a) (i) Calculate: (A) the horizontal component of the initial velocity of the sponge; Space for working and answer (B) the vertical component of the initial velocity of the sponge. Space for working and answer 1 1 page 07 MARKS DO NOT WRITE IN THIS MARGIN 1. (a) (continued) (ii) Calculate the time taken for the sponge to reach its maximum height. Space for working and answer (iii) The sponge takes a further 0·45 s to travel from its maximum height until it hits the teacher. Determine the height h above the ground at which the sponge hits the teacher. Space for working and answer (b) The student throwing the sponge makes the following statement. “If the sponge is thrown with a higher speed at the same angle from the same height then it would take a shorter time to hit the teacher in the same place.” Explain why the student’s statement is incorrect. 3 4 2 [Turn over page 08 MARKS DO NOT WRITE IN THIS MARGIN 2. An internet shopping company is planning to use drones to deliver packages. package drone (a) During a test the drone is hovering at a constant height above the ground. The mass of the drone is 5·50 kg. The mass of the package is 1·25 kg. (i) Determine the upward force produced by the drone. Space for working and answer 3 page 09 MARKS DO NOT WRITE IN THIS MARGIN 2. (a) (continued) (ii) The package is now lowered using a motor and a cable. A battery supplies 12 V across the motor. The resistance of the motor is 9∙6 Ω. Calculate the power dissipated by the motor. Space for working and answer (iii) While the package is being lowered the cable breaks. The upward force produced by the drone remains constant. Describe the vertical motion of the drone immediately after the cable breaks. Justify your answer. [Turn over 3 2 page 10 MARKS DO NOT WRITE IN THIS MARGIN 2. (continued) (b) To carry a package with a greater mass two drones are used as shown. not to scale cable 3∙4 kg drone 35° package drone cable 35° The drones are hovering at a constant height above the ground. The mass of the package suspended from the two drones is 3·4 kg. Determine the tension in each cable. Space for working and answer 4 page 11 [Turn over for next question DO NOT WRITE ON THIS PAGE page 12 DO NOT WRITE IN THIS MARGIN 3. A student sets up an experiment to investigate a collision between two vehicles on a frictionless air track. not to scale card vehicle Y motion sensor vehicle X to computer air track Vehicle X of mass 0·75 kg is travelling to the right along the track. Vehicle Y of mass 0·50 kg is travelling to the left along the track with a speed of 0·30 m s-1. The vehicles collide and move off separately. A computer displays a graph showing the velocity of vehicle X from just before the collision to just after the collision. velocity (m s−1) time (s) 1∙00 0∙90 0∙80 0∙70 0∙50 0∙60 0∙40 0∙30 0∙20 0 0∙10 0∙60 0∙50 0∙40 0∙30 0∙20 0∙10 0 page 13 MARKS DO NOT WRITE IN THIS MARGIN 3. (continued) (a) Show that the velocity of vehicle Y after the collision is 0·42 m s-1. Space for working and answer (b) Determine the impulse on vehicle Y during the collision. Space for working and answer [Turn over 2 3 page 14 MARKS DO NOT WRITE IN THIS MARGIN 3. (continued) (c) Explain how the student would determine whether the collision was elastic or inelastic. 2 page 15 MARKS DO NOT WRITE IN THIS MARGIN 4. A stunt is being carried out during the making of a film. A car is to be driven up a ramp on a moving lorry by a stunt driver, who will attempt to land the car safely on the roof of a second moving lorry. The car is to stop on the roof of the second lorry while this lorry is still moving. Using your knowledge of physics, comment on the challenges involved in carrying out the stunt successfully. [Turn over 3 page 16 MARKS DO NOT WRITE IN THIS MARGIN 5. Hubble’s Law states that the universe is expanding. The expanding universe is one piece of evidence that supports the Big Bang theory. (a) State one other piece of evidence that supports the Big Bang theory. (b) A student plots some of the original data from the 1929 paper by Edwin Hubble and adds the line shown in order to determine a value for the Hubble constant H0. 40 25 500 000 35 15 400 000 30 600 000 300 000 0 200 000 recessional velocity (m s−1) 100 000 distance (× 1021 m) 20 10 5 0 The student calculates the gradient of their line and obtains a value for the Hubble constant of 2∙0 × 10−17 s−1. The age of the universe can be calculated using the relationship 0 1 age of universe H = 1 page 17 MARKS DO NOT WRITE IN THIS MARGIN 5. (b) (continued) (i) Calculate the age of the universe, in years, obtained when using the student’s value for the Hubble constant. Space for working and answer (ii) The current estimate for the age of the universe is 13∙8 × 109 years. (A) State why the value obtained in (b)(i) is different from the current estimate for the age of the universe. (B) Suggest a change that the student could make to their graph to obtain a value closer to the current estimate for the age of the universe. (c) It has been discovered that the rate of expansion of the universe is increasing. State what physicists think is responsible for this increase. 2 1 1 1 [Turn over page 18 MARKS DO NOT WRITE IN THIS MARGIN 6. An experiment is set up to demonstrate a simple particle accelerator. vacuum metal cross + fluorescent screen − anode cathode 1·6 kV (a) Electrons are accelerated from rest between the cathode and the anode by a potential difference of 1·6 kV. (i) Show that the work done in accelerating an electron from rest is 2·6 × 10-16 J. Space for working and answer (ii) Calculate the speed of the electron as it reaches the anode. Space for working and answer 2 3 page 19 MARKS DO NOT WRITE IN THIS MARGIN 6. (continued) (b) As the electrons travel through the vacuum towards the fluorescent screen they spread out. In the path of the electrons there is a metal cross, which is connected to the positive terminal of the supply. The electrons that hit the cross are stopped by the metal. Electrons that get past the metal cross hit a fluorescent screen at the far side of the tube. When electrons hit the fluorescent screen, the screen glows. shadow of metal cross glowing fluorescent screen The potential difference between the anode and the cathode is now increased to 2∙2 kV. This changes what is observed on the screen. Suggest one change that is observed. You must justify your answer. [Turn over 2 page 20 MARKS DO NOT WRITE IN THIS MARGIN 6. (continued) (c) A student builds a model of a particle accelerator. The model accelerates a small ball on a circular track. A battery-operated motor accelerates the ball each time it passes the motor. To cause a collision a plastic block is pushed onto the track. The ball then hits the block. ball track motor plastic block Using your knowledge of physics comment on the model compared to a real particle accelerator, such as the large hadron collider at CERN. 3 page 21 DO NOT WRITE IN THIS MARGIN 6. (c) (continued) [Turn over page 22 MARKS DO NOT WRITE IN THIS MARGIN 7. A student uses a gold-leaf electroscope to investigate the photoelectric effect. A deflection of the gold leaf on the electroscope shows that the metal plate is charged. The student charges the metal plate on the electroscope and the gold leaf is deflected. 0 20 40 60 80 metal rod gold leaf metal plate gold-leaf electroscope (a) Ultraviolet light is shone onto the negatively charged metal plate. The gold-leaf electroscope does not discharge. This indicates that photoelectrons are not ejected from the surface of the metal. Suggest one reason why photoelectrons are not ejected from the surface of the metal. 1 page 23 MARKS DO NOT WRITE IN THIS MARGIN 7. (continued) (b) The student adjusts the experiment so that the gold-leaf electroscope now discharges when ultraviolet light is shone onto the plate. The work function for the metal plate is 6∙94 × 10−19 J. (i) State what is meant by a work function of 6∙94 × 10−19 J. (ii) The irradiance of the ultraviolet light on the metal plate is reduced by increasing the distance between the gold-leaf electroscope and the ultraviolet light source. State what effect, if any, this has on the maximum kinetic energy of the photoelectrons ejected from the surface of the metal. Justify your answer. [Turn over 1 2 page 24 MARKS DO NOT WRITE IN THIS MARGIN 7. (continued) (c) The graph shows how the kinetic energy of the photoelectrons ejected from the metal plate varies as the frequency of the incident radiation increases. The threshold frequency for the metal plate is 1∙05 × 1015 Hz. kinetic energy (J) frequency (× 1015 Hz) 1∙05 0 The metal plate is now replaced with a different metal plate made of aluminium. The aluminium has a threshold frequency of 0∙99 × 1015 Hz. Add a line to the graph to show how the kinetic energy of the photoelectrons ejected from the aluminium plate varies as the frequency of the incident radiation increases. (An additional graph, if required, can be found on page 45.) (d) Explain why the photoelectric effect provides evidence for the particle nature of light. 2 1 page 25 MARKS DO NOT WRITE IN THIS MARGIN 8. A student investigates interference of light by directing laser light of wavelength 630 nm onto a grating as shown. not to scale θ screen laser grating (a) A pattern of bright spots is observed on a screen. (i) Explain, in terms of waves, how bright spots are produced on the screen. (ii) The grating has 250 lines per millimetre. Calculate the angle θ between the central maximum and the third order maximum. Space for working and answer [Turn over 1 3 page 26 MARKS DO NOT WRITE IN THIS MARGIN 8. (a) (continued) (iii) The grating is now replaced by one which has 600 lines per millimetre. State the effect of this change on the pattern observed. Justify your answer. (iv) The interference pattern is produced by coherent light. State what is meant by the term coherent. 2 1 page 27 MARKS DO NOT WRITE IN THIS MARGIN 8. (Continued) (b) The student now shines light from the laser onto a £5 note. not to scale screen £5 note laser When it is shone through the transparent section of the note the student observes a pattern of bright spots on the screen. The diagram below shows the pattern that the student observes on the screen. Suggest a reason for the difference in the pattern produced using the £5 note and the pattern produced using the grating. [Turn over 1 page 28 MARKS DO NOT WRITE IN THIS MARGIN 9. A ray of monochromatic light is incident on a glass prism as shown. glass air incident ray 45·0° 45·0° 68·0° 22·0° 60·0° 60·0° 60·0° (a) Show that the refractive index of the glass for this ray of light is 1∙89. Space for working and answer (b) (i) State what is meant by the term critical angle. 2 1 page 29 MARKS DO NOT WRITE IN THIS MARGIN 9. (b) (continued) (ii) Calculate the critical angle for this light in the prism. Space for working and answer (iii) Complete the diagram below to show the path of the ray as it passes through the prism and emerges into the air. Mark on the diagram the values of all relevant angles. glass air incident ray 45·0° 45·0° 68·0° 22·0° 60·0° 60·0° 60·0° (An additional diagram, if required, can be found on page 45.) [Turn over 3 4 page 30 MARKS DO NOT WRITE IN THIS MARGIN 9. (continued) (c) A ray of white light is shone through the prism and a spectrum is observed as shown. screen violet red air glass white light The prism is now replaced with another prism made from a different type of glass with a lower refractive index. Describe one difference in the spectrum produced by this prism compared to the spectrum produced by the first prism. 1 page 31 MARKS DO NOT WRITE IN THIS MARGIN 10. In a laboratory experiment, light from a hydrogen discharge lamp is used to produce a line emission spectrum. The line spectrum for hydrogen has four lines in the visible region as shown. (a) The production of the line spectrum can be explained using the Bohr model of the atom. State two features of the Bohr model of the atom. [Turn over 2 page 32 MARKS DO NOT WRITE IN THIS MARGIN 10. (continued) (b) Some of the energy levels of the hydrogen atom are shown. E0 E1 −5·45 × 10−19 J E2 E3 E4 −21·8 × 10−19 J −2·42 × 10−19 J −1·36 × 10−19 J −0·871 × 10−19 J One of the spectral lines is due to electron transitions from E3 to E1. Determine the frequency of the photon emitted when an electron makes this transition. Space for working and answer 3 page 33 MARKS DO NOT WRITE IN THIS MARGIN 10. (continued) (c) In the laboratory, a line in the hydrogen spectrum is observed at a wavelength of 656 nm. When the spectrum of light from a distant galaxy is viewed, this hydrogen line is now observed at a wavelength of 661 nm. Determine the recessional velocity of the distant galaxy. Space for working and answer [Turn over 5 page 34 MARKS DO NOT WRITE IN THIS MARGIN 11. A student constructs a battery using a potato, a strip of copper and a strip of magnesium. potato magnesium copper The student then sets up the following circuit with the potato battery connected to a variable resistor R, in order that the electromotive force (e.m.f.) and internal resistance of the battery may be determined. potato battery r E R V A (a) State what is meant by the term electromotive force (e.m.f.). 1 page 35 MARKS DO NOT WRITE IN THIS MARGIN 11. (continued) (b) The student uses readings of current I and terminal potential difference V from this circuit to produce the graph shown. 180 0 160 20 140 40 120 700 100 600 80 500 I (μA) 400 V (mV) 300 60 200 100 0 Determine the internal resistance of the potato battery. Space for working and answer [Turn over 3 page 36 MARKS DO NOT WRITE IN THIS MARGIN 11. (continued) (c) The student connects a red LED and a blue LED, in turn, to the battery. The LEDs are forward biased when connected. The student observes that the battery will operate the red LED but not the blue LED. The diagram represents the band structure of the blue LED. electrons in valence band electrons in conduction band p-type n-type band gap LEDs emit light when electrons fall from the conduction band into the valence band of the p-type semiconductor. Explain, using band theory, why the blue LED will not operate with this battery. 1 page 37 [Turn over for next question DO NOT WRITE ON THIS PAGE page 38 DO NOT WRITE IN THIS MARGIN 12. A student carries out a series of experiments to investigate alternating current. (a) A signal generator is connected to an oscilloscope and a circuit as shown. green LED A signal generator red LED oscilloscope The output of the signal generator is displayed on the oscilloscope. div div The Y-gain setting on the oscilloscope is 1·0 V/div. The timebase setting on the oscilloscope is 0·5 s/div. page 39 MARKS DO NOT WRITE IN THIS MARGIN 12. (a) (continued) (i) Determine the peak voltage of the output of the signal generator. Space for working and answer (ii) Determine the frequency of the output of the signal generator. Space for working and answer (iii) The student observes that the red LED is only lit when the ammeter gives a positive reading and the green LED is only lit when the ammeter gives a negative reading. Explain these observations. 1 3 2 [Turn over page 40 MARKS DO NOT WRITE IN THIS MARGIN 12. (continued) (b) The signal generator is now connected in a circuit as shown. The settings on the signal generator are unchanged. The signal generator has negligible internal resistance. signal generator 68 Ω 82 Ω Determine the r.m.s. voltage across the 82 Ω resistor. Space for working and answer 5 page 41 MARKS DO NOT WRITE IN THIS MARGIN 13. A student sets up an experiment to investigate the pressure due to a liquid as shown. h meter pressure sensor liquid glass tube The pressure due to a liquid is given by the relationship p ρgh = where p is the pressure due to the liquid in pascals (Pa), g is the gravitational field strength in N kg−1, ρ is the density of the liquid in kg m−3, and h is the depth in the liquid in m. (a) The student initially carries out the investigation using water. The density of water is 1·00 × 103 kg m−3. Calculate the pressure due to the water at a depth of 0·35 m. Space for working and answer 2 [Turn over