Physicshomework XI-16th march Friday

1. A short-sighted person can see object lying between 10 cm and 20 cm from his eye clearly. (I) What should be the power of the lens he should use (ii) What will be the near point and far point with the lens used. 
2. A convex spherical mirror with a focal length of magnitude 24 cm is placed 20 cm to the left of a plane mirror. An object 0.25 cm tall is placed mid-way between the surface of the plane mirror and the vertex of the spherical mirror. The spherical mirror forms multiple images of the object. Where are two images of the object formed by the spherical mirror that are closest to the spherical mirror, and how tall is each image? 
3. An air bubble inside a glass slab(�=1.5) appears 6 cm when viewed from one side and 4 cm when viewed from opposite side. What is the thickness of slab. 
4. Two capacitors of capacitances 2�F and 5�F respectively are connected in series and combination connected momentarily across a 100V battery. The charged capacitors are now isolated and then connected in parallel, similar charged plates being together. What would be the resulting potential difference across the combination? 
5. Calculate the rms speed of oxygen molecules at STP, the molecular weight of Oxygen being 32. 
6. The silica cylinder of a radiant wall heater is 0.6 m long and has a radius of 5 mm. If it is rated as 1.5 KW, estimate its temperature when operating. (Stefan's constant = 6�10-8 wm-2K-4 ) 
7. A piece of gold-aluminum alloy weighs 100 gm in air and 80 gm in water. What is the weight of the gold in the alloy if the relative density of gold is 19.3 and that of aluminum is 2.5.  
8. What is the power output in horsepower of an electric motor turning at 4800 rev/mins and developing a torque of 4.3 Nm?
9. 
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Physicshomework XI for march 9/Friday

2. Emilie's potter's wheel rotates with a constant 2.25 rad/s2 angular acceleration. After 4 s the wheel has rotated through an angle of 60 rad. What was the angular velocity of the wheel at the beginning of the 4 s interval? 
3. A steel cable with cross-sectional area 3 cm2 has an elastic limit of 2.4�108 Pa. Find the maximum upward acceleration that can be given a 1200kg elevator supported by the cable if the stress is not to exceed 1/3 of the elastic limit. 
4. An earth satellite moves in a circular orbit with an orbital speed of 6200m/s. (a) Find the time of one revolution. (b) Find the radial acceleration of the satellite in its orbit. 
5. Water flows through a horizontal tube of length 20 cm and internal radius 0.081 cm under a constant head of the liquid 20 cm high. If 864 cm3 of water issues from the tube in 12 minutes, calculate the coefficient of viscosity of water. Density of water= 1 gm/cm3 , g = 981 cm/s2 
6. A 5.8 �F parallel plate air capacitor has a plate separation of 5 mm and is charged to a potential difference of 400 V. Calculate the energy density in the region between the plates. 
7. A parallel plate air filled capacitor has circular plates separated by 1.8 mm. The charge per unit area on each plate has magnitude 5.6pC/m2. What is the potential difference between the plates of the capacitor? 
8. Five moles of an ideal gas are kept at a constant temperature of 530C while the pressure of the gas is increased from 1 atm to 3 atm. Calculate the work done by the gas. 
   
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Physics homework XII-25th Feb Sunday

1. What is doppler effect? Find an expression for the change in apparent frequency when the source passes by the stationary observer.
2. Whistle of an approaching train is shriller. Why?
3. A tunning fork has two prongs. Why?
4. In which medium is the angle of polarization greater, rarer or denser?
5. Define a.c.power. Derive an expression for it. Also define power factor.
6. What is wattless current?
7. What do you mean by radiation hazard? What are its safety measures?
8. Give a brief account on "Energy sources of Nepal".
9. Explain the term artificial radio isotopes.
10. What do you mean by dark energy and dark matter?

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Physics homework XI-23rd Feb Friday

1. Derive an expression for the energy stored in a charged capacitor and also find energy density.
2. Obtain expressions for the equivalent capacitance when the capacitors are connected in series and parallel combination separately.
3. What are polar and nonpolar dielectic?
4. What is surface tension? Derive an expression for it using capillary rise method.
5. Explain why the liquid drops are spherical in shape?
6. Hot soup are tastier than cold one. Why?
7. Why has a gas two values of molar heat capacities?
8. What is adiabatic process? Derive an expression for the workdone in this process.
9. What is angular magnification? Obtain it for compound microscope when final image is formed at near point.
10. What is f-number of camera?

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Physics homework XII-18thFeb 2018-Sunday

1. What is Doppler's effect? Obtain an expression for the change in apparent frequency when an observer passes by a stationary source.
2. State the laws of radioactivity and derive decay equation.
3. What is green house effect?Discuss its effects, sources and the controlling measures.
4. Discuss the phase relationship between the voltage and current in a.c. circuit containing capacitor and resistor in series and hence derive an expression for the impedance of the circuit.
5. Why is a choke coil better than a resistor in an electrical appliances?
6. What is meant by impedance of an a.c. circuit?
7. What do you mean by curie?
8. What is acid rain? Explain.
9. What is global warming? Explain.
10. What are ultrasonic and infrasonic?
11. Which has a more direct influence on the loudness of a sound wave: the displacement amplitude or the pressure amplitude? Explain.
12. Bats catch their prey in the dark even when they don't see the prey. How can this happen?
13. A tuning fork has two prongs. why?
14. State Hubble's law and write the significance of Hubble's constant.
15. What are quarks? Write their names with charge they contained.

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Physics homework XI-16th feb 2018-friday

1.       What is the magnitude of an electric field, which will balance the weight of an electron on the             surface of earth?
2.       A parallel plate air capacitor of capacitance 2.45 pF has a charge of magnitude o.148 �C on each         plate. Find the potential difference and electric field intensity between the plates if the distance           between the plates is 5mm?
3.       Obtain the value of g from the motion of moon assuming that its period of rotation round the               earth is 27 days 8 hours and the radius of its orbit is 60.1 times the radius of the earth. Radius of         earth = 6.36�10⁶ m.
4.       A simple pendulum 4 m long swings with an amplitude of 0.2 m. compute the velocity of the               pendulum at its lowest point and its acceleration at the extreme ends.
5.       Angle of contact of mercury with glass is 135�. A narrow tube of glass having diameter 2mm is           dipped in a beaker containing mercury. By what height does the mercury go down in the tube               relative to the level of mercury outside? Surface tension of mercury = 0.547 Nm^-1 , Density of             mercury = 13600 kgm^-3
6.       The correct inflation of a tyre at 20� C is 2 kg/cm². After driving several hours, the driver checks        the tryes. If the tyre�s temperature is 50�C, what should be the pressure reading?
7.       If  earth shrinks, how will be the duration of a day affected?
8.       A body floats in a liquid contained in a beaker. The whole system falls under gravity. What is            the value of upthrust on the body due to liquid?
9.       A student claimed that thermometers are useless because a thermometer always registers its own         temperature. How would you respond?
10.   Why do we feel uncomfortable during very high relative humidity of air?
11.   Why does a refrigerator consume more power in summer than in winter to cool the same                     quantity  of food by same degree?

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