Formatting page ...
F.M 80 Tim e 2 Hrs PRE-BOARD-II EXAMINATION 2018-2019 SUBJECT: Physics (SCIENCE Paper 1) CLASS- X Answers 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 answers. 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 from this Section. Question 1 [2 x 5 = 10] a) A wasp of mass 20g flies vertically up at a speed of 50cm/sec. What is the power in its wings? b) What energy conversions take place in the following, when they are working: i) Electric toaster ii) Microphone c) To use a machine as a force multiplier, what type (class) of lever should preferably be used? Draw a sketch of such a lever. d) Differentiate between infra-red rays and ultra-violet rays in terms of their: i) action on photographic plate ii) uses e) The particles of mud fly off tangentially from the wheel of a moving vehicle. Why? Question 2 [2 x 5 = 10] a) Critical angle for glass-air pair is 42 . What do you mean by this statement? b) Write the factors on which focal length of a lens depends. c) An object is placed in front of a lens between its optical center and the focus and forms a virtual, erect and diminished image. i) Name the lens which formed this image ii) Draw a ray diagram for the above formation of image. d) The refractive index of diamond is 2.42. What is meant by this statement? e) i) How is the refractive index of a medium related to its real depth and apparent depth? ii) Which characteristic property of light is responsible for the blue colour of the sky? Question 3 [2 x 5 = 10] a) A radar is able to detect the reflected waves from an enemy s aeroplane after a time interval of 0.02 milliseconds. If the velocity of the waves is 3 x 10 8 ms-1, calculate the distance of the plane from the radar. 1 b) Two wires are of equal mass and material, but one has a length half of other. Calculate the ratio between their resistances. c) A nucleus does not contain electrons. How is then -particle emitted from the nucleus? Explain your answer by giving a chemical reaction. d) Why the rear view mirror of a motor bike starts vibrating at some particular speed of the bike? e) A coil carrying current when placed in a magnetic field, experiences a turning effect. i) Name a device that makes use of this effect. ii) State one way, non-electrical or magnetic, how the turning effect can be increased. Question 4 [2 x 5 = 10] 0 0 a) What mass of water at 100 C is to be added to 5 kg of water at 10 C to prepare a water bath at 300C? b) Why do pieces of ice added to a drink cool it much faster than ice-cold water added to it? c) Two resistors, R1 and R2, are first connected in series and then in parallel, across the same source. i) In which case, the current through the source is greater? ii) In which case, the rate of conversion of electrical energy to heat energy, in resistors, is more? d) How many alpha and beta particles are emitted when uranium nucleus 238U92 decays to lead 206Pb82? e) State the energy change which takes place when a magnet is moved inside a coil having a galvanometer at its ends. Name the phenomenon. SECTION II (40 Marks) Attempt any four questions from this Section. Question 5 [3 + 3 + 4 = 10] a) A world weight lifting record is held by Sergei Didyk of USSR. He lifted 261 kg to a height of 2.3 m in 4 s. Find i) the weight lifted by Didyk ii) the work done by him iii)the power developed by him. (Take g=10ms -2) b) Ramesh applies a force of 6 kgf to draw a 4.8 kg bucket of water from a well using a single fixed pulley. Assuming that all of the extra force applied is to overcome frictional force, calculate force of friction, mechanical advantage and efficiency. c) Figure below shows the combination of a movable pulley P 1 with a fixed pulley P2 used for lifting up a load W. i) State the function of the fixed pulley P 2. ii) If the free end of the string moves through a distance x, find the distance by which the load W is raised. iii) Calculate the force to be applied at C, to raise the load W=20 kgf, neglecting the weight of the pulley P1 friction. Question 6 [3 + 3 + 4 = 10] a) In the given ray diagram, AO is a ray of light incident on a rectangular glass block PQRS, which is silvered at the surface RS. Complete the ray diagram. State which image will be the brightest. 2 b) A lens forms an inverted image of size two times that of the object, on a screen placed at a distance 90 cm from the object. Find: i) the position of the lens ii) the magnification of image with its sign iii) the kind of lens and its focal length c) A lens is used as a reading glass. i) Name the lens used. ii) Draw a ray diagram to support your answer. iii) What should be done to increase the magnification of the lens? Question 7 [3 + 3 + 4 = 10] a) i) A ray of light PQ is incident normally on the face AB of an equilateral glass prism. Complete the ray diagram showing its emergence into air after passing through the prism. Take critical angle for glass=42 0 ii) What are totally internally reflecting prisms? b) What change, if any, would you expect in the characteristics of a musical sound when we modify: i) Its frequency ii) Its amplitude iii) Its waveform. c) A man fires a gun and hears its echo after 5s. The man then moves 310m towards the hill and fires his gun again. This time he hears the echo after 3s, calculate: i) the speed of sound ii) the original distance of the man from the hill. Question 8 [3 + 3 + 4 = 10] a) What purpose is served by the terminals of a three way pin? Why the uppermost pin is made longer and thicker? b) In the figure below, A, B, C are three ammeters. The ammeter B reads 0.5A. (All the ammeters have negligible resistance). Calculate: i) readings of ammeters A and C. ii) total resistance of the circuit. 3 c) An electric bulb is marked 200V, 100W. i) What do the markings mean? ii) Another bulb is marked 50 W, 200V which one has a coil of higher resistance? iii) What will be the energy used by the 1 st bulb, if used for 10 hrs a day for 10 days? iv) What is the cost of the energy used, if 1kWh is priced at Rs 1.60? Question 9 [3 + 3 + 4 = 10] a) 65 g of ice at 00C is added to 150 g of water at 500C and the mixture attains the temperature of 10 0C. What is the value of the latent heat of fusion of ice? b) The graph represents a cooling from higher temperature to a lower temperature. i) What is the fusion point of the substance? ii) What happens in the region DE? iii) Why is the region DE shorter than the region BC? c) State three consequences of high specific heat capacity of water. Question 10 [3 + 3 + 4 = 10] a) What is the function of a step-up transformer? Draw a labeled diagram to show the various Components of a step-up transformer. Name one device, where both step-up and step-down transformers are implemented. b) i) When does the nucleus of an atom become radioactive? ii) How is the radioactivity of an element affected when it undergoes a chemical change to form a chemical compound? iii) Name the most harmful of the radioactive radiations. Explain why? c) A nucleus AXZ emits an alpha particle followed by a gamma emission and then two beta particle to form X3. Write the nuclear changes in form of a nuclear reaction and show that the nuclei X and X 3 are isotopes. 4 5
|
