## Important Physics Exam Question paper 2072 (2015) HSEB exam paper

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**Answer in brief, any six questions**

- Check dimensionally the correctness of the stroke’s formula, F=6
- A woman in an elevator lets go of her briefcase but it does not fall to the floor. How does the particle’s speed not change ?
- If there is a net force acting on a particle in uniform circular motion, Why does the particle’s speed not change?
- An astronaut inside a small space ship orbiting around the earth does experience any gravity. But an astronaut on the moon Which is also orbiting around the earth does experience gravity. Why ?
- Does the center of gravity of a solid body always lie within the material of the body explain.
- Small air bubbles rise slowly while big bubbles rise rapidly through the liquid. Why ?

- Answer in brief, any two Questions:
- a) Groundnuts are fried along with sand, Why ?

b)Dews are formed in the clear night but not in the cloudy night. Explain why?

c)Explain the significance of second law thermodynamics.

- Answer in brief, any one Question:
- a) A concave mirror is often used as an aid for applying cosmetics to the face, why?

b)Sun glasses have curved surfaces but their power is zero, Why ?

- Answer, in brief any one question:

a)What is potential gradient? How is it related with the electric field intensity?

b)Can we give any desired charge to a capacitor ? Explain

**Group B **

5.Answer any three Questions:

- a) Define angle of repose. Show that the angle of repose and the angle of friction are equal for the given pair of surfaces.

b)What is escape of velocity ? Derive an expression for the escape velocity on the surface of the eath .

- c) Define moment of inertia. Obtain an expression for the escape velocity on the surface of the earth.

d)What is capillarity? Deduce a relation for the height of liquid column rise in a capillary tube when one end in the liquid.

6.Answer any two Questions:

- a) Define cofficients of real and apparent expansions of a liquid, and establish a relation between them.

b)Using the postulates of kinetic theory of gases, deduce an expression for the pressure exerted by an ideal gas on the walls of the container.

c)What is an isothermal process? Derive the relation PV^r= Constants Where symbols have their usal meanings.

a)What is chromatic aberration in lens? Deduce the condition for achromation in two lenses in contact.

b)Describe the structure and working of an astronomical telescope at normal adjustment with a suitable ray diagram. Also calculate its magnifying power.

8.) Answer any one Questions:

- a) What is electrostatic induction ? Explain with necessary diagrams, a method of charging a body positively by induction ?
- b) State and explain Gauss’s theorem and use it to find the electric field due to a charged sphere at a point

(i) Outside the sphere (ii) inside the Sphere

**Group “C”**

**9.Answer any three numerical Questions**

- a) A Batter hits a baseball so that it leaves the bat with an initial speed 37m/s at an angle of 53*. Find the position of the ball and the magnitude and direction of its velocity after 2 seconds. Treat the baseball as a projectile.

b)A little red wagon with mass7 kg moves in a straight line on a frictionless horizontal surface. It has initial speed of 4m/s and then is pushed 3m in the direction of the initial velocity by a force of 10N calculate the wagon’s final speed and the acceleration produced by the force.

- c) A body of mass 200gm is executing simple harmonic motion with amplitude of 20mm. The maximum force which acts upon it is 0.80N

calculate its maximum velocity and its period of oscillation.

- d) A uniform steel wire of density 8000kg m-3 weighs 20gm and is 2.5m long. Ot lengthens by 1mm when stretched by a force of 80N. Calculate the value of the young’s modulus of steel and the energy stored in the wire.

10.Answer any two numerical questions:

a)In an experiment on the specific heat of metal, a 200gm block of metal at 150*c is dropped in a copper calorimeter of mass 270gm containing 150cm3 of water at 27*c. The final temperature is 40*c calculate the specific heat of the metal.

- b) A pot with a steel bottom 8.5mm thick rest on a hot stove. The area of the bottom of the pot is 0.15m^2. The water inside the pot is at 100*c and 390gm of water is evaporated every 3 minute. Find the temperature of lower surface of the pot which is in contact with the stove.

c)A Carnot’s engines has 25% efficiency with a sink at 9*c. By How many degrees should the temperature of the source be increased in order to raise the efficiency to 70%?

- A ray of light is refracted through a prism of angle 60*. Find the angle of incidence so that the emergent ray just grazes in the second race. Refractive index of material of the prism is 1.45

12.Two capacitors of capacitances 4Uf and 12Uf respectively, are connected in series. The combination is then connected momentailu across 200v. Find the charge and potential difference across each capacitor?