## Sunday, 12 February 2017

### QUESTIONS ON THERMODYNAMICS ,OSCILLATION ANS WAVES

1.      Define Capillarity and angle of contact. Derive an expression for the ascent of a liquid in a capillary tube.
2.      Give the principle of working of venturimeter. Obtain an expression for volume of liquid flowing through he tube per second.

3.      Define the coefficients of linear expansion. Deduce relation between it and coefficient of superficial
expansion and volume expansion.
4.      Define (i) Specific heat capacity (ii) Heat capacity (iii) Molar specific heatcapacity at constant pressure and at constant volume and write their units.
5.      What is latent heat? Give its units. With the help of a suitable graph,explain the terms latent heat of
fusion and latent heat of vaporisation.
6. Show that there is always an excess pressure on the concave side of the meniscus of a liquid. Obtain  an  expression for the excess pressureinside (i) a liquid drop (ii) soap bubble (iii) air bubble inside a  liquid.
7. State and prove Bernoullis theorem. Give its limitation. Name any two application of the
principle.
8. Define terminal velocity. Obtain an expression for terminal velocity of a sphere falling through a viscous liquid. Use the formula to explain theobserved rise of air bubbles in a liquid.
9. On what factors does the rate of heat conduction in a metallic rod in the steady state depend. Write the   necessary expression and hence define the coefficient of thermal conductivity. Write its unit and dimensions.
10. Distinguish between conduction, convection and radiation.
11. Describe briefly carnot engine and obtain an expression for its efficiency.
12. Define adiabatic process. Derive an expression for work done during adiabatic process.
13. Why a gas has two principle specific heat capacities? What is the
significance of Cp – Cv and Cp/Cv where symbols have usual meaning.

14. What are the basic assumptions of kinetic theory of gases? On their basis derive an expression
for the     pressure exerted by an ideal gas.

15. What is meant by mean free path of a gas molecule? Derive an expression for it.
16. Given that P =1/3pc2 where P is the pressure, ρ is the density and c is the rms. Velocity of gas

molecules. Deduce Boyle’s law and Charles. Law of gases from it.
17.Show that for a particle in linear simple harmonic motion, the acceleration is directly proportional to its displacement of the given instant.
18. Show that for a particle in linear simple harmonic motion, the average kinetic energy over a period of oscillation, equals the average potential energy over the same period.
19.Deduce an expression for the velocity of a particle executing S.H.M when is the particle velocity (i) Maximum (ii) minimum?
20. Draw (a) displacement time graph of a particle executing SHM with phase angle φ equal to zero (b) velocity time graph and (c) acceleration time graph of the particle.
21.Show that for small oscillations the motion of a simple pendulum is simple harmonic. Derive an expression for its time period.
22.Distinguish with an illustration among free, forced and resonant oscillations.
23. In reference to a wave motion, define the terms
(i) amplitude (ii) time period
(iii) frequency (iv) angular frequency
(v) wave length and wave number.
24. Derive expressions for the kinetic and potential energies of a simple harmonic oscillator. Hence show that the total energy is conserved in
S.H.M. in which positions of the oscillator, is the energy wholly kinetic or wholly potential?
25. What are standing waves? Desire and expression for the standing waves. Also define the terms node and antinode and obtain their positions.
26. Discuss the formation of harmonics in a stretched string. Show that in case of a stretched string the first four harmonics are in the ratio 1:2:3:4,
27. Give a qualitative discussion of the different modes of vibration of an open organ pipe.
28. Describe the various modes of vibrations of a closed organ pipe.
29. What are beats? How are they produced? Briefly discuss one application
for this phenomenon.

### CBSE CLASS11 PHYSICS THERMAL PROPERTIES OF MATTER, THERMODYNAMICS, KINETIC THEORY OF GASES, OSCILLATION AND WAVES

THERMAL PROPERTIES, THERMODYNAMICS AND KINETIC THEORY OF GAS
1.  Two stars radiate maximum energy at wavelength, 3.6 × 10–7 m and 4.8× 10–7m respectively.
What is the ratio of their temperatures? 4/3
2. A metal piece of 50 g specific heat 0.6 cal/g°C initially at 120°C is dropped in 1.6 kg of water at  25°C. Find the final temperature or mixture. θ = 26.8oc
3. A iron ring of diameter 5.231 m is to be fixed on a wooden rim of diameter 5.243 m both initially
at 27°C. To what temperature should the iron ring be heated so as to fit the rim (Coefficient of
linear  expansion of    iron is1.2 × 105 k–1? 218oC
4. 100g of ice at 0°C is mixed with 100 g of water at 80°C. The resulting temperature is 6°C.   Calculate .heat of  fusion of ice. 68 cal/g.
5. Calculate heat required to convert 3kg of water at 0°C to steam at 100°C Given specific heat    capacity of H20 =   4186J kg–1 k–1 and latent heat of steam = 2.256 × 106 J/kg Total heat =   8023800J
6. A body re-emits all the radiation it receives. Find surface temperature of the body. Energy received per unit area per unit time is 2.835 watt/m2 and α = 5.67 × 10–8 W m–2 k–4 85 k.

7. A thermodynamic system is taken from an original state to an intermediate state by the linear
process shown in Fig.Its volume is then reduced to the original value from E to F by an isobaric

process. Calculate the total work done by the gas from D to E to F.
450 J

8. What is the coefficient of performance (β) of a carnot refrigerator working between 30°C and   0oC? 9.1
9. Calculate the fall in temperature when a gas initially at 72°C is expanded suddenly to eight times         its originalvolume. (γ = 5/3) 86.25 k
10. Refrigerator is to maintain eatables kept inside at 9oC. If room temperature is 36°C calculate the
coefficient of  performance. 10.4
11. A perfect carnot engine utilizes an ideal gas the source temperature is 500K and sin temperature
is 375K. If the engine takes 600k cal percycle from the source, calculate
(i) The efficiency of engine                       25%
(ii) Work done per cycle                            450 k cal
(iii) Heat rejected to sink per cycle.           450 k cal

12. Ten mole of hydrogen at NTP is compressed adiabatically so that its temperature become 400oC
How much work is done on the gas? What is the increase in the internal energy of the gas R =
8.4 J mol–1 K–1 γ = 1.4            8.4×104 J

13. An air bubble of volume 1.0 cm3 rises from the bottom of a lake 40 m deep at a temperature of
12°C. To what volume does it grow when itreaches the surface which is at a temperature of
35oC? 5.3×10–6m3
14. A vessel is filled with a gas at a pressure of 76 cm of mercury at a certain temperature. The
mass of the gas is increased by 50% by introducing more gas in the vessel at the same
temperature. Find out the resultant  pressure of the gas. 114 cm of Hg.

15. One mole of a monoatomic gas is mixed with three moles of a diatomic gas. What is the
molecular specific heat of the mixture at constant volume? Take R = 8.31/mol–1 K–1. 18.7 J
mole–1 K–1

16. An oxygen cylinder of volume 30 litre has an initial gauge pressure of 15 atmosphere and a
temperature of 27°C. After some oxygen is withdrawn from the cylinder, the gauge pressure
drops to 11 atmosphere and its temperature drop to 17°C. Estimate the mass of oxygen taken out         of thecylinder(R = 8.31/mol–1 k–1) 0.140 kg. (molecular mass of O2 = 32)

17. 0.014 kg of nitrogen is enclosed in a vessel at a temperature of 27°C. How much heat has to be
transferred to the gas to double the rms speed of its molecules. 2250 cal.
OSCILLATION AND WAVES
18. Find the period of vibrating particle (SHM), which has acceleration of 45cm s–2, when
displacement from mean position is 5 cm 2.095 s
19. A 40 gm mass produces on extension of 4 cm in a vertical spring. A mass of 200 gm is  suspended at its bottom  and left pulling down. Calculate the frequency of its vibration. 1.113 s–1
20. The acceleration due to gravity on the surface of the moon is 1.7 ms–2.What is the time period of   a simple pendulum on the moon, if its time period on the earth is 3.5 s? [g = 9.8 ms–2] 8.4s
21. A particle executes simple harmonic motion of amplitude A.(i) At what distance from the mean   position is its kinetic energy equal to its potential energy? (ii) At what points is its speed half the maximum speed?
22. A particle executes S.H.M of amplitude 25 cm and time period 3s. What is the minimum time
required for the particle to move between two points 12.5 cm on either side of the mean position?
0.5 s
23. The vertical motion of a huge piston in a machine is approximately S.H.M with a frequency of 0.5  s–1. A block of 10kg is placed on the piston. What is the maximum amplitude of the piston’s  S.H.M. for the block and  piston to remain together? 0.993m
24. At what temperature will the speed of sound be double its value at 273°K? 1092°K
25. A spring balance has a scale that reads from 0 to 50 kg. The length of the scale is 20 cm. A body
suspended from this spring, when displaced and released, oscillates with a period of 0.60 s. What
is the weight of the body? 218.93 N.
26. If the pitch of the sound of a source appears to drop by 10% to a moving person, then determine
the velocity of motion of the person. Velocity of sound = 330 ms–1. 200 ms-1
27. A string of mass 2.5 kg is under a tension of 200N. The length of the stretched string is 20m. If a        transverse jerk is struck at one end of the string, how long does the disturbance take to reach the
other end? 0.5 s
28. The equation of a plane progressive wave is given by the equation y = 10 sin 2π(t – 0.005x) where y and x are in cm and t in seconds.Calculate the amplitude, frequency, wave length and velocity of the wave. 10 cm, 200 cm, 200 ms–1, 1 HZ

29. The length of a wire between the two ends of a sonometer is 105 cm. Where should the two bridges be placed so that the fundamental frequencies of the three segments are in the ratio of 1 : 3 : 15 ? Hence the bridges should be placed at 75 cm and (75 + 25 =) 100 cm from one end.

30. A wire stretched between two rigid supports vibrates in its fundamental mode with a frequency 45 Hz. The mass of the wire is 3.5×10–2 kg andits linear density is 4.0×10–2 kg m–1 What is (a) the speed of transverse wave on the string and (b) the tension in the string? 78.75 ms–1

31. A steel rod 100 cm long is clamped at its middle. The fundamental frequency of longitudinal
vibrations of the rod as given to be 2.53 kHz.What is the speed of sound in steel? 5.06 × 103 ms–1