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Bunts Sangha R.N.S Vidyaniketan Vijayanagar, Bengaluru-40 III Preparatory Examination 2020-21 Sub: PHYSICS CLASS 10[ICSE] M ax M arks : 80 Date: 0 .0 .2021 Time: 2 hour ______________________________________________________________________________________ Answers to this paper must be written on the paper 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. Attempt all questions from section A and section B. The intended marks for questions or parts of questions are given. ______________________________________________________________________________________ SECTION A ATTEM PT ALL THE QUESTIONS QUESTION 1 (5 = ) 1. a) What happens to the power of an object when the object moves in a circular motion b) What happens to the power if the time for doing a work is reduced from t second to second? 10 2. Define the following (a) Becquerel rays (b) background radiations 3. Write two difference between natural and forced vibrations 4. Where does the position of centre of gravity lies for a) Uniform hexagonal lamina b) Boomerang 5. A scooter mechanic can open a nut by applying 120N force while using a lever of 50cm in length. How long handle is required if he wishes to open it by applying a force of only 40N QUESTION 2 (5 = ) 1. Draw a ray diagram for the following cases a) To show the first focus position of convex lens b) To show the second focus position of concave lens 2. What change, if any, would you expect in the characteristics of a musical sound when we increase : (a) its frequency (b) its amplitude 3. 2kg of water is contained in 1250W kettle. Calculate the time taken for the temperature of water to rise from 250C to 1000C 4. An object 6cm tall is placed on the principal axis of a convex lens. Its 3cm tall image is formed on the screen placed at a distance of 30cm from the lens. Calculate the focal length of the lens. 5. a) Write the mathematical form of Joules law of heating b) How should the electric lamps in a building be connected? QUESTION 3 (5 = ) 1. A child hears an echo from a cliff 4 second after the sound from a powerful cracker is produced. How far away is the child from the cliff? Given speed of sound in air is 340ms-1 2. a) What do you mean by the statement efficiency of a machine is 60% b) Why is a machine not 100% efficient?
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