NEB - GRADE XI Question 2076 (2019) | Physics

NEB-GRADE XI

2076 (2019)

Physics

Time: 3 hrs.                               Full Marks:75

Candidates are required to give their answers in their own words as far as practicable.

You may use the following values of physical constants wherever necessary:

Acceleration due to gravity (g) = 10ms ^-2

Young’s modulus for copper = 1.2×10 ¹¹ Nm ^-2

Young’s modulus for steel = 2×10 ¹¹ Nm ^-2

Cubical expansivity of glass = 1.2×10 ^{-5 / o} C

Cubical expansivity of mercury = 18×10 ^{-5 / o} C

Specific heat capacity of copper = 400 Jkg ^-1 k ^-1

Specific heat capacity of water = 4200 Jkg ^-1 k ^-1

Ratio of molar heat capacities (γ ) = 1.4

Permittivity of free space (∈ _o ) =8.85×10 ^-12 C ² N ^-1 m ^-2

Group ‘A’

1. Answer in brief, any six questions. 6×2=12

1. The energy of a photon is given by Ε = hf. Find the dimension and unit of Plank’s constant h, where f is the frequency of radiation.


2. From a flying aeroplane a body should be dropped in advance to hit thetarget, why?


3. A light body and a heavy body have the same momentum. Which one will have greater Kinetic energy? Explain.


4. A person sitting in an artificial satellite of the earth feels weightlessness,but a person standing on moon has weight through the moon is a satellite of the earth. Why ?


5. The passengers in a small boat are not allowed to stand, why ?


6. If the ice on the polar caps of the earth melts, how will it affect the duration of the day? Explain.


7. Why does hot soup taste better than cold soup?

2. Answer in brief, any two questions. 2×2=4

1. The latent heat of vaporization is much larger than the latent heat of fusion of a substance. Why?


2. Why does it take longer time to dry wet clothes in rainy summer than insunny winter ?


3. The internal energy of a compressed gas is less than that of a rarefied gas at the same temperature. Why?

3. Answer in brief, any one question. 2

1. The sun is less bright in morning and evening as compared to that atnoon although its distance from the observer is almost the same. Why?


2. When white light is dispersed by a prism, red light appears at the top of the spectrum where as violet at the bottom. Why?

4. Answer in brief, any one question. 2

1. Bits of paper are attracted to an electrified comb, even though they have no net charge. How is this possible?


2. Can two electric lines of force intersect each other? Explain.

Group ‘B’

5. Answer any three questions. 3×4=12

1. What is escape velocity ? Derive an expression for it on the surface of the earth.


2. Define angle of friction and angle of repose. Establish a relation between them.


3. Define moment of inertia. Derive an expression for the moment of inertia of thin uniform rod about an axis through its centre and perpendicular to its length.


4. What is simple harmonic motion ? Calculate the total energy of a particle executing simple harmonic motion.

6. Answer any two questions. 2×4=8

1. State Newton’s law of cooling. Use it to find the specific heat capacity of a unknown liquid.


2. Derive an expression for the pressure exerted by an ideal gas on the basis of Kinetic theory.


3. Describe the working principle of diesel engine with the help of PV diagram.

7. Answer any one question. 4

1. Define lateral shift and derive an expression for it due to a parallel edged glass slab.


2. Explain the construction and working of a compound microscope withfinal image at near point. Also, derive an expression for its magnifying power.

8. Answer any one question. 4

1. State and explain Gauss’s law in electrostatics and use it to determinethe electric field intensity due to a line charge.


2. What is capacitance of a capacitor ? Derive a relation for the energystored in a capacitor when it is charged to a potential difference of V volts.

Group ‘C’

9. Answer any three numerical questions. 3×4=12

1. A disoriented physics professor drives 3.25 km north, then 4.75 km west and then 1.50 km south. Find the magnitude and direction of the resultant displacement.


2. A bob of mass 200 gram is whirled in a horizontal circle of radius 50cm by a string inclined at 30 ⁰ to the vertical. Calculate the tension in the string and the speed of the bob in the horizontal circle.


3. A copper wire and a steel wire of the same crosssectional area and of length 1m and 2 m respectively are connected end to end. A force is applied, which stretches their combined length by 1cm. Find how much each wire is elongated.


4. Eight spherical rain drops of the same mass and radius are falling down with a terminal speed 5 cms ^-1 . If they coalesce to form one big drop, what will be its terminal speed ?

10. Answer any two numerical questions. 2×4=8

1. A glass flask of volume 400 cubic centimeter  is just filled with mercury at 0 ⁰ C. How much mercury will overflow when the temperature of the system rises to 80 ⁰ C.


2. A copper calorimeter of mass 300 gm contains 500gm of water at temperature 15 ⁰ C. A 560 gm block of aluminium at temperature 100 ⁰ C is dropped in the calorimeter and the temperature is observed to increase to 22.5 ⁰ C . Find the specific heat capacity of aluminium.


3. A certain volume of dry air at NTP is allowed to expand five times of its original volume under adiabatic condition. Calculate the final pressure and temperature.

11. A convex lens of focal length 24 cm and of refractive index 1.5 is totally immersed in water of refractive index 1.33. Find its focal length in water.  4

12. Three equal charges 1.8×10 ^-6 C each are located at the corners of an equilateral triangle ABC of side 10 cm. Calculate the electric potential due to these charges at the mid point of AB.  3

The End