Full Marks:- 100 | Pass Marks :- 35 | Time:- 3 hrs. Attempt all the questions. • You may use the following values of physical constants wherever necessary. • Specific gravity of steel= 7.8 • Latent heat of ice=80 calgm-1 • Latent heat of steam= 540 cal/gm • Linear expansivity of glass= 1.8 X 10-6 K-1 • Volume expansivity of mercury= 1.8 X 10-4 K-1 Group ‘A’ 1. Answer in brief any six questions. [6x2=12] (a) How does the kinetic energy of a body change if its momentum is halved? (b) If the sun some how collapsed to form a black-hole, what effect would this event have on the orbit of the earth? (c) Can the direction of the velocity of a body be changed when its acceleration is constant? (d) If A and B are non-zero vectors, is it possible for A X B and A.B both to be zero? Explain. (e) In hot air ballooning, a large balloon is filled with air heated by a gas burner at the bottom. Why must the air be heated? (f) A man drops his briefcase in an elevator but it does not fall to the floor.What can be concluded about the situation? (g) An ice cube floats in a glass of water. When the ice melts, will the water level in the glass rise, fall or remain unchanged?Explain. 2. Answer in brief any two questions. [2x2=4] (a) Frozen water pipes often burst, will a merucry thermometer break if the temperature of the thermometer is brought below the freezing point of mercury? (b) If you add heat to an object, do you necessarily increase its temperature? Justify your answer. (c) Why are the polar regions much cooler than the equitorial regions despite the fact that the polar regions are periodically tilted towards sun? 3. Answer in brief any one question. [1x2=2] (a) Can a convex mirror ever form real image? Justify your answer. (b) A large object when taken away from your eye appears smaller. Why? 4. Answer in brief any one question. [1x2=2] (a) Why is it dangerous to take shelter under a tree during lightning? (b) Can two electric lines of force ever intersect each other? Explain. Group ‘B’ 5. Answer any three questions. [3x4=12] (a) State the parallelogram law of vector addition.Derive the expression for the magnitude and direction of the resultant of two vectors inclined at an angle H from each other. (b) What is geo stationay satellite? Obtain an expression for the total energy of a satellite orbitting round the earth? (c) State the principle of conservation of linear momentum.How does the Newton’s third law of motion lead to the principle of conservation of linear momentum? (d) Derive an expression for the energy stored in a stretched rod.Define the term energy density of a body under strain. 6. Answer any two questions. [2x4=8] (a) Define linear and cubical expansivities of solids. Derive an expression for the variation in density of solid when its temperature is raised from H1 oC to H2 oC . (b) Define adiabatic process in thermodynamics. Show that: PVr=constant where symbols have their usual meanings. (c) Describe the working of petrol engine with the help of P-V diagram. 7. Answer any one question. [1x4=4] (a) What is long sightedness? Discuss the possible causes of long sightedness. Explain,how this defect can be remedied. (b) Derive an expression for lens maker’s formula. 8. Answer any one question. [1x4=4] (a) State Gauss Theorem. Use this theorem to find the electric field intensity due to a plane charged conductor. (b) How can a number of capacitors be connected to increase and decrease the effective capacitance? Find the respective expressions for the effective capacitance in each case. Group ‘C’ 9. Solve any three questions. [3x4=12] (a) A man wishes to swim across a river 600m wide. If he can swim at the rate of 4km/h in still water and the river flows at 2kn/h.Then in what direction must he swim to reach a point exactly opposite to the starting point and when will he reach it? (b) A ballet dancer spins with 2.4rev/sec with her arms outstretched when the moment of inertia about the axis of rotation is I. With her arms folded,the moment of inertia about the same axis becomes 0.6I.Calculate the new rate of spin. (c) A cricket ball of mass 145 gm is moving with velocity of 14m/s and is being hit by a bat , so that the ball is turned back with a velocity of 22m/s. The force of blow acts on the ball fr 0.015 sec.Find the average force exerted by the bat on the ball. (d) Castor oil at 20oC has a coefficient of viscosity 2.42Ns/m2 and density 940Kg/m3. Calculate the terminal velocity of a steel ball of radius 2mm falling under gravity in the oil. 10. Solve any two questions. [2x4=8] (a) Air at a temperature of 273K and a pressure of 1.01 X 105 N/m2 pressure contains 2.7X1025 molecules per cubic meter.How many molecules per cubic meter will be there at a place where the temperature is 223 K and the pressure is 1.33X10-4 N/m2? (b) 10gm of steam at 100oC is passed into a mixture of 100gm of water and 10gm of ice at 0oC.Find the resulting temperature of the mixture. (c) A glass vessel of volume 50cm3 is filled with mercury and is heated from 20oC to 60oC.What volume of mercury will overflow? 11. An object to the left of a lens is imaged by the lens on a screen 30 cm to the right of the lens. When the lens is moved 4cm to the right, th screen must be moved 4cm to the left to refocus the image.Determine the focal length of the lens. [4] 12. Two charges +1X10-6 C and -4X10-6C are separated by a distance of 2m.Determine the position of the null point. [3]
Posted on: Tue, 26 Nov 2013 09:32:37 +0000
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