Session Ending Exam, 2021-22
Class-XI
Subject -Physics
Max. Marks 35 Max. Time 2 Hours
General Instructions:
(i) There are 12 questions in all. All questions are compulsory.
(ii) This question paper has three sections: Section A, Section B and Section C.
(iii) Section A contains three questions of two marks each, Section B contains eight questions of three marks each and Section C contains one case study-based question of five marks.
(iv) There is no overall choice. However, an internal choice has been provided in one
question of two marks and two questions of three marks. You have to attempt only one of the choices in such questions.
(v) You may use log tables if necessary but use of calculator is not allowed.
SECTION – A
Q.1 The amplitude of a simple harmonic oscillator is doubled. How does this affect –
(i) periodic time
No change
(ii) maximum velocity
Doubled
(iii) maximum acceleration
Doubled
(iv) maximum energy
Four times
Q.2 The frequency of first overtone of a closed organ pipe is same as that of first overtone of an open organ pipe. What is the ratio of their lengths?
Formula for first overtone closed pipe
Formula for first overtone open pipe
Correct answer (3/4)
Q.3 Show that the number of beats produced per second is equal to the difference between the
frequencies of the two superposing waves.
OR
A set of 24 tuning forks is arranged in a series of increasing frequencies. If each fork gives 4
beats per second with the preceding one and the last sounds the octave of the first, find the
frequencies of the first and the last forks.
Frequency of first fork (92)
Frequency of last fork (184)
SECTION B
Q.4 Find the amount of heat required to convert 2 kg of ice at -10°C into steam at 100°C.
Given specific heat capacity of ice is 0.5 cal/g °C, specific heat capacity of water is 1 cal/g °C,
latent heat of fusion of ice is 80 cal/g & latent heat of vaporization of water is 540 cal/g).
Amount of heat Q = 1450 kcal
Q.5 Find an expression for the excess of pressure inside a liquid drop of radius R. Find the
excess pressure inside a soap bubble 5mm in diameter. Surface tension of soap solution is 1.6
N/m.
2560 pascal
OR
A liquid is in a streamline flow through a pipe of non-uniform cross section. Prove that the sum of its kinetic energy, pressure energy and potential energy per-unit volume remains constant.
Q.6 (i) Draw a graph to show the variation of kinetic energy, potential energy and total energy of a simple harmonic oscillator with displacement.
(ii) Find the value of displacement at which the kinetic energy and potential energy are equal.
A/√2
Q.7 A harmonic wave along a string is described by the equation y(x, t) = 0.005sin(80x-3t) in which the numerical constants are in SI units .
Find the amplitude, wavelength, frequency and speed of the wave
Is this a travelling wave or stationary wave? In which direction the wave advances in the
medium?
Amplitude =0.005m
Wavelength = 2π/80m
Time period =2π/3s
Frequency =3/2π
Speed = 3/80m/s
Travelling wave in the positive X direction
OR
The equation for stationary wave is represented by
y(x, t) = 2 Sin (2π x/3) Cos (30πt) Calculate amplitude, wavelength and velocity of the
wave
What are the frequencies of first harmonic and third harmonic modes of oscillations in a closed organ pipe?
Amplitude =1 m
Wavelength = 3 m
Time period = (1/15) s
Speed = 45m/s
First harmonic or fundamental frequency in a closed pipe = v/4L
Third harmonic or First overtone is 3v/4L
Q.8 Discuss stress-strain graph for a loaded steel wire and hence explain the terms elastic limit, yield point, permanent set, elastic hysteresis and tensile strength.
Q.9 On the basis of kinetic theory of gases, how does a gas exert pressure and derive an
expression for the pressure exerted by an ideal gas
Q.10 What is an adiabatic process? Give example. What are the essentials conditions for an
adiabatic process to occur? Write first law of thermodynamics for an adiabatic process
Q.11 One gram of water at 373 K is converted into steam at the same temperature at normal
pressure. The volume of 1 cm3 of water becomes 1671 cm3 on boiling. Calculate the change on the internal energy of the system if the heat of vaporization is 540 cal/g
SECTION C
Q.12 Oil is carried through pipes from one place to another place. It is made sure that the flow of oil in pipes should be steady so that there is no danger of the damage of the pipe. Assume that an oil flows through a horizontal pipe of length 2.0 m and radius 50 cm. The amount of the oil collected at one end of the pipe is 5.0 x 10−3 kg/s. Assume that density of oil is 0.5 x 103 kg/m3 and coefficient of viscosity of oil at 30 °C is 0.02 Pa-s.
Based on the above facts, answer the following questions
(A) The volume of the oil flowing per second is
a) 1x 10−6 m3 /s
b) 1x 10−5 m3 /s
c) 1×10−4 m3 /s
d) 1 m3 /s
(B) The velocity of flow of oil in the pipe is
a) 1.0 x 10−5 m/s
b) 1.3 x 10−5 m/s
c) 2.0 x 10−5 m/s
d) 2.3 x 10−5 m/s
(C) Pressure difference between the ends of the pipe is
a) 1.63 x 10−5 Pa
b) 2.63 x 10−5 Pa
c) 4 x 10−6 Pa
d) 6 x 10−6 Pa
(D) Reynolds number is
a) 0.00163
b) 0.0163
c) 0.163
d) 1.63
(E) Flow of oil in the pipe is
a) laminar
b) turbulent
c) unstable
d) laminar as well as turbulent