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Physics Work, Energy, Power Question paper

1 pages, 25 questions, 8 questions with responses, 8 total responses,    0    0
Nilanjan Das
St. Xavier's College (SXC), Kolkata
Master of Science Biotechnology
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ICSE Physics Test WORK, POWER & ENERGY By Nilanjan Das ( xaveriannilanjan@outlook.com ) F.M. 40 Time: 1 hr Section: I (Attempt all the questions) (20 marks) 1. a) State the energy changes that take place in the following: 4 i) Water in the freezer of a refrigerator turns into ice ii) Petrol engine of a running motor car iii) A microphone iv) Water from the dams rotates the turbines of a dynamo. b) Show that p = 2mEK , where the symbols have their usual meanings. 3 c) A stone of mass 15 g is thrown vertically upwards with a velocity of 200 cm s-1. Find the Potential energy at its maximum height. 3 2. a) If your electricity bill says that your family has consumed 400 kWh of electrical energy, how many joules are actually consumed? b) Explain the following: Kinetic energy is always positive. c) How fast should a man weighing 60 kg run so that his kinetic energy is 750 J ? d) If the power of a motor is 40 kW, at what speed it can raise a load of 20,000 N ? e) Is work a scalar or a vector quantity? 2 2 2 3 1 Section: II (Attempt any two questions) (20 marks) 3. a) State the conditions for no work . 2 b) A 1.0 kW motor drives a pump which raises water through a height of 15 m. Calculate the mass of water lifted per second. (Assuming the system is 100% efficient). 3 c) Fill in the blanks: 3 i) The velocity of a moving body is increased four times, Hence its kinetic energy will be ___ times the initial kinetic energy. ii) 1 Horse-power = _____ Watt. iii) An example of conversion of mechanical energy to electrical energy is ___________. d) An electron and a proton have their masses in the ratio 1 : 1840. What will be the ratio of their Kinetic Energy, if they have equal momenta? 2 4. a) A bullet of mass 25 g moving with a velocity of 600 m/s, strikes a wooden target and penetrates 50 cm into the target. Calculate the resisting force of the target. 4 b) State Einstein s mass-energy equivalence relation. 1 c) Schematically represent how hydroelectric energy is generated. 3 d) Choose the correct alternative: 2 i) An example of non-conventional source of energy is A. Wood B. Nuclear energy C. Coal D. Petrol ii) Power of an agent is measured in A. J m B. N m C. J s-1 D. N s-1 5. a) A block of mass 3 kg is pulled 5 m up a smooth plane, inclined at an angle 300 to the horizontal, by a force of 25 N, parallel to the plane. Find the velocity of the block when it reaches the top. 3 b) Write briefly: The Sun in the Ultimate source of Energy. 2 c) A body is falling freely from a distance h above the ground. Show that at every point of the trajectory, its motion obeys the Law of Conservation of Energy. 5

 

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