1. Relative density of silver is 10.8. The density of water is 10 3 Kgm -3 . What is the density of silver in SI unit? Ans: Relative density of silver = 10.8 Relative density of water = 10 3 Kgm -3 Density of silver = Relative density of silver x Relative density of water = 10.8 x 10 3 Kgm -3 2. Is potential energy a vector or a scalar quantity? Ans: Potential energy is a scalar quantity. 3. (i) Give any two examples of longitudinal waves.(ii) What is the most essential property of a wave motion and why? Ans: (a) i. Waves produced in air. ii. When a freely suspended spring is pulled downwards and released, longitudinal waves are produced. (b) The most essential property of a wave motion is its frequency. Frequency of a wave is its inherent characteristic and does not change by the change in temperature, pressure or change in medium. 4. (a) Calculate the work done in lifting 200 kg of water through a vertical height 6 meter. (Assuming g = 10m
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