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SN Kansagra School MECHANICS UNIT TEST Standard: 10 Maximum Marks: 40 Date: 31st August 2016 Time: 60 minutes Question 1 a) Mention one unit of energy, apart from joule, that is used to express the following. [2] b) A ring is melted and made into a sphere. Describe what happens to its centre of gravity. [2] c) Define kgf. How is it related to the SI unit of force? [2] i. Heat energy ii. Electrical energy iii. Energy released on combustion of fat iv. Energy of an electron d) Give an example of a Class 1 lever whose mechanical advantage is lesser than 1. Describe the benefit of the machine named by you. [2] e) The number of teeth on the driver and the follower gear are 36 and 12 respectively. i. What is the use of such a gear train? [1] ii. Justify your answer to the question above. [1] a) A ball is thrown upwards. Explain why the work done by the force of gravity is negative. [2] Question 2 b) A ball is dropped from a height of 4 m. i. What is the maximum height to which the ball can bounce back after hitting the ground? [1] ii. Why is the actual height lesser than the one stated by you above? c) Why is the mechanical advantage of an inclined plane always greater than 1? [1] [2] d) A metal ball is placed upon a compressed spring. Explain why the metal ball accelerates when the spring is released. [2] e) Why is centrifugal force said to be a fictitious force? [2]
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