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St. Francis Xavier School Rehearsal Examination (2017 18) Subject Physics Class X Time 2 hrs F.M. 80 Answer to this paper must be written on the paper provided separately. You will NOT be allowed to write during the first 15 minutes. This time is to be spent in reading the question paper. The time given at the head of this Paper is the time allowed for writing the answer. Section I is compulsory. Attempt any four questions from Section II. The intended marks for questions or parts of questions are given in brackets [] Section I (40 MARKS) (Attempt All Questions) Question 1: [2X5 = 10] a) A force is applied on (i) a non-rigid body and (ii) a rigid body. How does the effect of the force differ in the above two cases? b) A metallic ball is hanging by a string from a rigid support. Draw a neat labelled diagram showing the forces acting on the ball and the string. c) (i) What is the weight of a body placed at the centre of the earth? (ii) What is the principle of an ideal machine? d) Is it possible to have an accelerated motion with a constant speed? Explain. e) (i) When does a force do work? (ii) What is the work done by the moon when it revolves around the earth? Question 2: [2X5 = 10] a) Calculate the change in the kinetic energy of a moving body if its velocity is reduced to 1/3 rd of the initial velocity. b) State the energy changes in the following devices while in use : (i) A loud speaker, (ii) A glowing electric bulb. 1 This question paper consists of 5 pages c) i) What is nuclear energy? (ii) Name the process used for producing electricity using nuclear energy. d) State one important advantage and disadvantage each of using nuclear energy for producing electricity. e) Complete the sentences: (i) The conversion of the part of energy into an undesirable form is called ................... (ii) For a given height h, ................. the length l of the inclined plane, lesser will be the effort required. Question 3: [2X5 = 10] a) Draw the diagram given below and clearly show the path taken by the emergent ray. b) (i) What is consumed using different electrical appliances, for which electricity bills are paid? (ii) Name a common device that uses electromagnet. c) (i) A ray light passes from water to air. How does the speed of light change? (ii) Which colour of light travels fastest in any medium except air? d) Name the factors affecting the critical angle for the pair of mediad. e) (i) Name a prism required for obtaining a spectrum of ultraviolet light. (ii) Name the radiations which can be detected by a thermopile. Question 4: [2X5 = 10] a) Why is the colour red used as a sign of danger? b) (i) What are mechanical waves? (ii) Name one property of waves that do not change when wave passes from one medium to another. c) Find the equivalent resistance between the points A and B. 2 This question paper consists of 5 pages d) 50g of metal piece at 27oC requires 2400 J of heat energy so as to attain a temperature of 327oC. Calculate the specific heat capacity of the metal. e) Define the term heat capacity and state its S.I. unit. Section II (40 MARKS) (Attempt any four Questions) Question 5: [4 + 3 + 3 = 10] a) (i) A man having a box on his head, climbs up a slope and another man having an identical box walks the same distance on a leveled road. Who does more work against the force of gravity and why? (ii) Two forces each of 5 N act vertically upwards and downwards respectively on the two ends of a uniform meter rule which is placed at its mid-point as shown in the diagram. Determine the magnitude of the moment of these forces about the midpoint. b) (i) A body is thrown vertically upwards. Its velocity keeps on decreasing. What happens to its kinetic energy as its velocity becomes zero. (ii) Draw a diagram to shown how a single pulley can be used so as to have its ideal M. A. = 2. c) Derive a relationship between mechanical advantage, velocity ratio and efficiency of a machine. 3 This question paper consists of 5 pages Question 6: [4 + 3 + 3 = 10] a) (i) Light passes through a rectangular glass slab and through a triangular glass prism. In what way does the direction of two emergent beams differ and why? (ii) Ranbir claims to have obtained an image twice the size of the object with a concave lens. Is he correct ? Give a reason for your answer. b) A lens forms an erect, magnified and virtual image of an object. (i) Name the lens. (ii) Draw a labeled ray diagram to show the image formation. c) (i) Define the power of a lens. (ii) The lens mentioned in part (b) above is of focal length 25cm. Calculate the power of the lens. Question 7: [4 + 3 + 3 = 10] a) A type of electromagnetic wave has wavelength 50 oA. (i) Name the wave. (ii) What is the speed of wave in vacuum? (iii) State one use of this type of wave. b) What is meant by the terms (i) Amplitude , (ii) Resonance, if a sound wave. c) A person standing between two vertical cliffs and 480 m from the nearest cliff shouts. He hears the first echo after 3 s and second echo 2 s later. Calculate: i) The speed of the sound ii) The distance of the other cliff from the person. d) (i) State one important property of waves used for echo depth sounding. (ii) A radar sends a signal to an aircraft at a distance of 30 km away and receives it back after 2 x 10-4 second. What is the speed of the signal? Question 8: [4 + 3 + 3 = 10] a) Two resistance of 4 Ohm and 6 Ohm are connected in parallel to a cell to draw 0.5 A current from the cell. (i) Draw a labeled circuit diagram showing the above arrangement. (ii) Calculate the current in each resistor. b) What is an ohmic resistance? Two copper wires are of same length, but one is thicker than other (1) Which wire will more resistance? (2) Which wire will have more specific resistance? 4 This question paper consists of 5 pages c) (i) Two sets A and B, of three bulbs each, are glowing in two separate rooms. When one of the bulbs in set A is fused, the other two bulbs also cease to glow. But in set B, when one bulb fuses, the other two bulbs continue to glow. Explain why this phenomenon occurs. (ii) Why do we prefer arrangement of set B for house circuiting? Question 9: [4 + 3 + 3 = 10] a) Heat energy is supplied at constant rate of 100g of ice at 0oC. The ice is converted into water at 0oC in 2 minutes. How much time will be required to raise the temperature of water from 0oC to 20oC? [ Given: specific heat capacity of water = 4.2 J g-1 oC-1, specific latent heat of ice = 336 J g-1 ] b) Specific heat capacity of substance A is 3.8 J g-1 K-1 whereas the specific heat capacity of substance B is 0.4 J g-1 K-1. (i) Which of the two is a good conductor of heat? (ii) How is one led to the above conclusion? (iii) If substances A and b are liquids, then which one would be more useful in car radiators. c) (i) State any two measures to minimise the impact of global warming. (ii)What is green house effect? Question 10: [4 + 3 + 3 = 10] a) (i)Draw a simple labeled diagram of d. c. electric motor. (ii)What is the function of the split rings in a d. c. motor? (iii)State one advantage of a. c. over d. c. b) A nucleus 24Na11 emits a beta particle to change into magnesium (Mg). (i)Write the symbolic equation for the process. (ii)What are the numbers 24 and 11 called? (iii)What is the general name of 24Mg12 with respect to 24Na11 ? c) (i)Define radioactivity . (ii)Define nuclear fission. (iii)Define nuclear fusion. 5 This question paper consists of 5 pages
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