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BHAGATJI MEMORIAL MODEL SCHOOL, CLASS-IX, SCIENCE PA-2, , Q.1 Write the chemical formula:, a) Sodium carbonate b) Ammonium chloride, , 2, , Q.2 A) Calculate the number of molecules in 8g of O2., B) Calculate the number of moles is 52g of He (helium)., , 2, , Q.3 Write the name and symbol of element that is:, a) most malleable and ductile, b) a constituent of water and most abundant element in universe, c) best conductor of electricity, d) liquid at room temperature, Q.4 Write the difference between:, a) ‘G’ and ‘g’, b) mass and weight, , 2, , 2, , Q.5 State the Universal law of gravitation. Derive its expression., , 2, , Q.6 If the distance between two objects is increased four times, then how, many times will the mass of one of the objects be changed to maintain the, same gravitational force?, , 2, , Q.7 An object is thrown up with a velocity of 20 m/s. Find the maximum, 2, height attained by it and the total time taken by it to return back. Take ‘g’ as 10, m/s2., Q.8 Give one example of each: a) positive work b) zero work done, , 2, , Q.9 A ball of mass 0.5 kg is thrown up with a velocity of 15 m/s. Find its, potential energy at the highest point., , 2, , Q.10 Convert 250 KWh into Joules. And Write Mathematical Expressions for, Kinetic Energy and Potential Energy., 2