L.35 PRE-LEAVING CERTIFICATE EXAMINATION, 2016 PHYSICS ORDINARY LEVEL TIME 3 HOURS Answer three questions from Section A and five questions from Section B. Relevant data are listed in the Formulae and Tables booklet, which is available from the Superintendent. 2016.1 L.35 1/12 page 1 of 12
Answer three questions from this section. Each question carries 40 marks. SECTION A (120 marks) 1. In an experiment to verify the principle of conservation of momentum, a student measured the mass of two objects (A and B). One object (A) was set moving at constant velocity and collided with the second object (B) at rest. After the collision, the two objects stuck together. Measurements were taken to determine the velocities before and after the collision. The following are the values that were measured or calculated. Mass of A... 250 g Mass of B... 200 g Velocity before collision... 0.240 m s 1 Velocity after collision... 0.133 m s 1 (i) Draw a labelled diagram of the apparatus used in the experiment. (9) (ii) How did the student determine the velocity of an object in this experiment? (12) (iii) Calculate the momentum of object A before the collision. (9) (iv) Calculate the momentum of both objects after the collision. (6) (v) Explain how these results verify the principle of conservation of momentum. (4) 2. A student carried out an experiment to obtain the calibration curve of a thermometer based on a particular thermometric property. The following is an extract from her report. I placed the thermometer, based on the thermometric property that I was calibrating, in water at 0 C. I measured the temperature of the water using a standard thermometer and I measured the value of the thermometric property of my thermometer. I heated the water steadily and took measurements of the thermometric property every 10 C. The results I obtained are given in the table. Temperature ( C) 0 10 20 30 40 50 60 Thermometric property 18 22 27 33 39 46 54 (i) Draw a labelled diagram of the apparatus used in this experiment. (12) (ii) What is a suitable thermometer to use as a standard thermometer? Name a suitable thermometric property for the student s thermometer. (9) (iii) Plot a graph, on graph paper, of the thermometric property against temperature. Put temperature on the X-axis. (12) (iv) Use the graph to estimate the temperature when the value of the thermometric property is 48. (7) 2016.1 L.35 2/12 page 2 of 12
3. In an experiment to measure the wavelength of a monochromatic light source using a diffraction grating, a number of angular measurements were taken. The number of lines per mm on the diffraction grating is 400. (i) Draw a labelled diagram of the apparatus that may have been used in the experiment. (12) (ii) What is monochromatic light? Give an example of a monochromatic light source. (6) (iii) Explain how the angular measurements were taken. (9) (iv) What is the distance between each line in the diffraction grating? (6) (v) How is the wavelength of light calculated? (7) 4. In an experiment to investigate the relationship between current I and potential difference V for a filament bulb, the following data was recorded. V (V) 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 I (A) 1.3 2.4 3.0 3.5 3.8 4.0 4.1 4.1 (i) Name the instruments used to measure the current and potential difference values. (6) (ii) Where are these instruments positioned in the circuit in relation to the filament bulb? (6) (iii) Plot a graph, on graph paper, of the current against potential difference (put potential difference on the X-axis). (12) (iv) Does a filament bulb obey Ohm s law? Explain your answer. (7) (v) Use the graph to find the value of the resistance of the bulb when the potential difference across the bulb 4.5 V. (9) 2016.1 L.35 3/12 page 3 of 12
Answer five questions from this section. Each question carries 56 marks. SECTION B (280 marks) 5. Answer any eight of the following parts (a), (b), (c), etc. (a) State Newton s first law of motion. (b) A car accelerates from 20 m s 1 to 50 m s 1 in 2 seconds. What is the acceleration of the car? (c) What change is observed in the sound wave of the siren of a police car as it travels towards a stationary observer? (d) Define specific heat capacity. (e) Name a pair of complementary colours. (f) The glass in an optical fibre has a refractive index of 1.46. Calculate the critical angle for the glass in the optical fibre. (g) What is the purpose of a miniature circuit breaker (MCB) in an electrical circuit? (h) Calculate the amount of heat that is given off every second from a coil of wire whose resistance is 200 Ω and which is carrying a current of 4 A. (i) Identify the numbers represented by X and Y in the following alpha decay of radium: 228 X 4 Ra Ra+ He 88 Y 2 (j) From the list below, identify the scientist who developed the theory that electrons can only occupy certain energy levels around the nucleus of an atom. Bohr Einstein Rutherford Röntgen (8 7) 2016.1 L.35 4/12 page 4 of 12
6. Define pressure. (6) A man and a woman are walking together on soft ground. The man has a mass of 85 kg and is wearing flat shoes that have an area of 0.06 m 2 in contact with the ground. The woman has a mass of 65 kg and is wearing high heels that have an area of 0.02 m 2 in contact with the ground. (i) Find the weight of the man and the woman. (9) (ii) Calculate the pressure exerted by the woman on the ground. (6) (iii) Calculate the pressure exerted by the man on the ground. (6) (iv) Why is the woman more likely than the man to sink in the soft ground? (4) The pressure exerted on any object underwater varies with depth. (i) State Boyle s law. (6) (ii) How does Boyle s law explain why a bubble gets bigger as it rises towards the surface of a lake? (9) (iii) A fish starts at a depth of 20 m in water and rises to 1 m below the surface. What is the change in pressure on the fish as it makes this rise? (10) (density of water = 1000 kg m 3 ; acceleration due to gravity, g = 9.8 m s 2 ) 2016.1 L.35 5/12 page 5 of 12
7. What is meant by refraction of light? State one of the laws of refraction of light. (12) Lenses are one of the most common applications of the refraction of light. They are found in eyes, glasses, magnifying glasses and more complex instruments such as microscopes and telescopes. There are two types of lenses: convex and concave. Concave lenses always produce virtual images, but convex lenses produce virtual images only when the object is inside the focus. (i) What type of image is produced when the object is outside the focus in a convex lens? How does this type of image differ from a virtual image? (6) (ii) Draw a ray diagram showing how a virtual image is produced in a concave lens. (9) (iii) Why is a concave lens not suitable for use as a magnifying glass? (4) Light is focused onto the retina in an eye by a combination of a cornea and a lens. The distance from the lens to the retina is approximately 1.8 cm. (iv) Draw a diagram of the structure of the eye. (9) (v) How does the eye focus on objects at different distances? (6) (vi) Calculate the focal length of the lens/cornea combination if a person views an object at a distance of 15 cm from the eye. (10) 8. State Faraday s law of electromagnetic induction. (9) Describe a laboratory experiment to demonstrate Faraday s law. (12) A coil of wire is moved from a position where a magnetic flux of 8 Wb cuts the coil to a different position, where a magnetic flux of 18 Wb cuts the coil in 0.25 s. What is the electromotive force (emf) induced in the coil? (9) Transformers are devices based on electromagnetic induction. They are used to increase (step-up transformer) or decrease (step-down transformer) the values of a.c. voltages. (i) Draw a labelled diagram of a transformer. (9) (ii) Explain why a transformer does not work if a constant d.c. voltage is applied to the input coil. (9) (iii) The input coil of a transformer has 150 turns and the output coil has 750 turns. Calculate the output voltage if the voltage across the input coil is 230 V. (8) 2016.1 L.35 6/12 page 6 of 12
9. Define resistance. Name an instrument which measures resistance. (9) Thermistors and light-dependent resistors (LDRs) are types of resistors used in electrical circuits and have many applications. What is the difference between the operation of a thermistor and an LDR? (9) Give a use for (i) a thermistor and (ii) an LDR. (6) Draw the electrical circuit symbol for an LDR. 12 V (6) A thermistor is placed in series with a fixed resistor of resistance 400 Ω as shown. At a certain time the resistance of the thermistor is 1000 Ω. A Ten minutes later the resistance of the thermistor has changed to 600 Ω. 400 Ω What would have caused the change in the resistance of the thermistor during the 10-minute period? (6) (i) Calculate the total resistance and hence the current flowing in the circuit when the thermistor has a resistance of 1000 Ω. (9) (ii) Calculate the change in current in the circuit after 10 minutes. (11) 10. Nuclear energy can be produced by nuclear fusion and nuclear fission. Nuclear fusion releases the energy that causes all stars, including our Sun, to exist for billions of years. Nuclear fission releases the energy that is produced in nuclear reactors in many countries throughout the world. (i) What is the difference between nuclear fusion and nuclear fission? (12) (ii) Name the two gases that are present in the Sun and are involved in nuclear fusion. (6) (iii) How do scientists know that these gases are present in the Sun? (6) (iv) Why is the Sun only expected to burn for approximately another 5 billion years? (6) (v) What is the role of (a) the control rods and (b) the moderator in a nuclear reactor? (12) (vi) Name a suitable fuel for use in a nuclear reactor. (6) (vii) How does Einstein s formula E = mc 2 explain how energy is released in a nuclear reactor during nuclear fission? (8) 2016.1 L.35 7/12 page 7 of 12
11. Read the following passage and answer the accompanying questions. Many musical instruments consist of an air column enclosed inside a hollow metal tube. Though the metal tube may be more than a metre in length, it is often curved upon itself one or more times in order to conserve space. If the end of the tube is uncovered such that the air at the end of the tube can freely vibrate when the sound wave reaches it, then the end is referred to as an open end. If both ends are uncovered or open, the musical instrument is said to contain an open-end air column. A variety of instruments operate on the basis of open-end air columns; examples include the flute and the recorder. Even some organ pipes serve as open-end air columns. A number of different harmonics can be set up in open-end air columns in metal tubes. Each of the harmonics observed is a multiple of the fundamental frequency, which is dependent primarily on the length of the tubes; the longer the tube, the lower the fundamental frequency. (Adapted from www.physicsclassroom.com, Lesson-5, Open-End-Air-Columns) (a) Give two examples of musical instruments that have open-end air columns. (b) Explain why it is not possible to generate a musical note that is 1.5 times greater than the fundamental frequency possible for a musical instrument that contains an open-end air column. (c) What primarily determines the fundamental frequency of a musical instrument with open-end air columns? (d) Draw a diagram showing a standing wave in a tube opened at both ends, when it is vibrating at its fundamental frequency. (e) What do (i) the nodes and (ii) the antinodes on the standing wave diagram you have drawn in part (d) represent? (f) If the fundamental frequency of the vibrations in a flute is 325 Hz, what is the frequency of the third harmonic? (g) Taking the speed of sound in air to be 340 m s 1, what is the wavelength of the musical note in the flute referred to in part (f) when it is vibrating at its fundamental frequency? (h) How would the fundamental frequency of the flute differ if a longer tube was used to make the flute? (8 7) 2016.1 L.35 8/12 page 8 of 12
12. Answer any two of the following parts (a), (b), (c), (d). (a) Define work. What is the unit of work? (9) Hossein Rezazadeh of Iran broke the Olympic record in weightlifting, when he lifted a mass of 263 kg from the ground to a height of 2.88 m above the ground. (i) Calculate the work done by Hossein when lifting the weight. (9) (ii) Calculate the power developed by Hossein, if he took 0.75 s to lift the weight. (6) (iii) What type of energy is the weight gaining while being lifted? (4) (acceleration due to gravity = 9.8 m s 2 ) (b) Distinguish between heat and temperature. What is the SI unit of temperature? (9) Heat can be transferred in a room by convection. What is convection? (6) Name one other method of heat transfer. (4) The photograph shows a cross section of an electric storage heater. Bricks with a high specific heat capacity are heated overnight by passing an electric current through a heating coil in the bricks. The bricks are surrounded by insulation. Why is insulation used to surround the bricks? (6) Name a material suitable for use as insulation. (3) 2016.1 L.35 9/12 page 9 of 12
(c) What is an electric field? (6) Describe an experiment to demonstrate the shape of the electric field between two charged plates. (9) Copy the diagram below and show the electric field lines produced due to a positive charge and negative charge near each other. (6) + Why are electric fields a problem for people who work with integrated circuits? (7) (d) What is the photoelectric effect? (6) The diagram shows a photocell connected in series to a galvanometer and a battery. A B Name the parts of the photocell labelled A and B. (6) Give an application of a photocell. (4) Radiation is incident on a zinc plate placed on the cap of a negatively charged gold leaf electroscope as shown. When visible light is incident on the zinc plate, no change is observed, but a change is observed when UV light is incident on the plate. (i) (ii) What change is observed when UV light is incident on the plate? Explain why this change is not observed for visible light. (9) Disc Radiation What change would be observed in the electroscope if the intensity of the visible light was increased? (3) Electroscope Zinc plate Gold leaves 2016.1 L.35 10/12 page 10 of 12
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