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3rd Preliminary Examination, 2018-19 Physics (2 hour) Grade: X Max Marks: 80 _____________________________________________________________________ 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. _____________________________________________________________________ Attempt all questions from Section A and any two questions from Section B. All working, including rough work, must be clearly shown and must be done on the same sheet as the rest of the answer. Omission of essential working will result in loss of marks. The intended marks for questions or parts of questions are given in brackets [ ]. _____________________________________________________________________ Section A (40 marks) (Attempt all questions from this section) Question 1 a) When a body is thrown vertically upward, its velocity keeps on [2] decreasing. What happens to its kinetic energy when its velocity b) becomes zero? A person can open a nut by applying a force of 120 N by using a lever [2] handle of length 40 cm. What should be the length of handle if he is able c) d) to open if he is able to open it by applying a force of 30N? Two bodies of masses m1 and m2 have equal kinetic energies. What will [2] be the ratio of their momenta? What is the work done in the following cases? (i) When moon makes a [2] complete revolution around the earth? (ii) A coolie carrying a load on his e) Question 2 a) head and walks on a level road. Define the term power. State it s SI unit. [2] Under what condition will a machine act as a (i) force multiplier (ii) [2]
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