NEB MODEL QUESTION FOR PHYSICS
Time : 3 hrs
Full Marks: 75
Pass marks: 27
Q.1. Answer in brief, any SIX questions. [2 X 6 = 12]
(a) What is the difference between accurate and precise measurements?
(b) A ball having a momentum P hits a bat and its momentum becomes –P. What is the change in the momentum of the ball?
(c) State the condition of equilibrium of a system of coplanar forces.
(d) Does the acceleration of a body moving in a circular path remain constant?
(e) Why is sand thrown on roads covered with snow?
A: Sand is thrown on roads covered with snow because when the tracks/ roads are covered with snow there is a reduction of friction between the tires of the vehicles and the road and during this situation it is dangerous to drive. when sand is thrown on the roads covered with snow then the friction increases between the road and the tire of the vehicle, and safe driving is possible.
(f) Since the moon is constantly attracted to the earth by the gravitational interaction, why doesn’t it crash into the earth?
(g) Explain in terms of breaking stress why the elephant has thicker legs as compared to human beings?
Q.2. Answer in brief, any TWO questions . [2 X 2 = 4]
(a) Why are two thin blankets warmer than a single blanket of double the thickness?
(b) Distinguish between saturated and unsaturated vapor pressure.
(c) Does the coefficient of linear expansion depend on length? Explain.
Q.3. Answer in brief, any ONE question : [1 X 2 = 2]
(a) Can a convex mirror ever from a real image? If so, explain with a diagram.
(b) What are grazing incidence and grazing emergence?
Q.4. Answer in brief, any ONE question : [2 X 1 = 2]
(a) A man inside an insulated metallic cage does not receive a shock when the cage is highly charged. Explain.
(b) Is it possible to charge a capacitor to any potential?
Q.5. Answer any THREE questions : [4 X 3 = 12]
(a) State the principle of conservation of linear momentum. How does Newton’s third law of motion lead to the principle of conservation of linear momentum?
(b) Prove that the total mechanical energy in the gravitational field is always conserved. Also explain conservation and non-conservative forces.
(c) What is SHM? Show that the motion of a bob of a simple pendulum is simple harmonic. Find its time period.
(d) What is capillarity? Deduce an expression for the rise of a liquid in a simple tube.
Q.6. Answer any TWO questions : [4 X 2 = 8]
(a) Define specific latent heat of fusion of a solid. Develop an expression for the latent heat of fusion of ice.
(b) Define the coefficient of thermal conductivity of a substance. Describe Searle’s method for the determination of the thermal conductivity of a good conductor.
(c) What is a Carnot engine? Derive an expression for its efficiency.
Q.7. Answer any ONE question : [ 4 X 1 = 4 ]
(a) Define the power of a lens. Derive the formula for the effective power of two thin lenses in contact.
(b) Describe the construction and working of a compound microscope and hence derive an expression for its magnifying power.
Q.8. Answer any ONE question : [4 X 1 = 4]
(a) State Gauss law. Apply it to obtain an expression for the electric field outside the charged special conductor.
(b) Find the equivalent capacitance of two capacitors when they are in (i) Series and (ii) parallel.
Q.9. Solve any Three numerical questions : [4 X 3 = 12]
(a) A ballet dancer spins with 2.4 revs/s 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 0.6 I. Calculate the new rate of spin.
(b) A canoe has a velocity of 0.4 m/s southeast relative to the earth. The canoe is on a river that is flowing 0.5 m/s east relative to the earth. Find the magnitude and direction of the velocity relative to the river.
(c) The sun has a mass 330,000 times that of the earth. For a person on earth, the average to the center of the sun is 23,500 times the distance to the center of the earth. In magnitude, what is the ratio of the sun’s gravitational forces on you to the earth’s gravitational forces on you?
(d) Castrol oil at 20oC has a coefficient of viscosity 2.42 Nsm-2 and a density of 940 Kgm-3. Calculate the terminal of a steel ball of radius 2.0 mm falling under gravity in the oil.
Q.10. Solve any TWO questions : [4 X 2 = 8]
(a) A ball of copper of specific heat capacity 400 Jkg-1K-1 weighting 400 gm is transferred from a furnace to 1 Kg of water at 20oC. The temperature of the water rises to 50oC. What is the initial temperature of the ball?
(b) An ideal gas initially at 4 atmospheres and 350 K is permitted to expand adiabatically to 1.5 times its initial volume. Find the final pressure and temperature to 1.5 times its initial volume. Find the final pressure and temperature if the gas is (i) monatomic and (ii) diatomic with Cv = 5/2 R.
(c) At what temperature will the average speed of oxygen molecules be sufficient so as to escape from the earth? Escape velocity from the earth is 11.2 Km/s and the mass of one oxygen molecules is 5.34 X 10-26 Kg.
Q.11. A microscope is focused on the upper surface of a glass plate. A second plate is then placed over the first. In order to focus on the bottom surface of the second plate, the microscope must be raised 1 mm. In order to focus on the upper surface, it must be raised 2 mm farther. Find the index of the retardation of the second plate.
Q.12. Two-point charges +1 µC is placed at a distance of 0.12 m apart. Determine the point on the line joining two charges where net forces acting on the positive charges is zero.