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PRE-BOARD EXAMINATIONS 2020-21 PHYSICS SCIENCE Paper-I Full Marks: 80 Time: 15 minutes reading 2 hours writing 30 minutes scanning and making PDF SECTION I (40 Marks) (Attempt all questions from this Section) Question 1 (a) Choose the correct option and give reason: The handle of the door is always near the (free end/hinge) of the door. (2) (b) State the energy changes that take place in the following when they are in use: (i) A photovoltaic cell (ii) A microphone. (2) (c) Where does the position of centre of gravity lie for: (i) Hollow cylinder (ii) Triangular lamina. (2) (d) A woman draws water from a well using a fixed pulley. The mass of the bucket and water together is 6.0 kg. The force applied by the woman is 70 N. Calculate the mechanical advantage. (2) (e) A body of mass 5 kg is moving with a velocity of 10m/s. What will be the ratio of its initial kinetic energy and final kinetic energy, if the mass of the body is doubled and its velocity is halved? (2) Question 2 (a) What should the angle between force and displacement be to get the: (i) Minimum work? (ii) Maximum work? (2) (b) State two advantages of using a right angled prism as a reflector rather than a plane mirror. (2) (c) The diagram shows a point source of light S, a lens L, and a plane mirror M. These are placed such that rays of light, form S return to it after reflection from M. (i) What is the distance OS called? (ii) To which point (left of S, on S, or right of S) will the rays return, if M is moved to the left and brought in contact with L. (2) (d) An object is placed in front of a convex lens such that the image formed has the same size as that of the object. Draw a ray diagram to illustrate this. (2) (e) During refraction of light at the surface of separation of two media, state the nature of media when (i) i > r (ii) r = 90 where i is the angle of incidence and r is the angle of refraction. (2) Protect by PDF Anti-Copy for Android (Update to Pro to remove watermark)
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