1
CH–17 Waves
Daily Practice Problem 07
REVISION:
Q3. A block is kept on a rough inclined plane,
Q1. An insect is at the bottom of a
as shown in the figure, remains at rest upto
hemispherical ditch of radius 1 m. it crawls
a maximum force 2 𝑁𝑁 down the inclined
up the ditch but start slipping after it is at
plane. The maximum external force up the
height ℎ from the bottom. If the coefficient of
inclined plane that does not move the block
friction between the ground and the insect is
is 10 𝑁𝑁. The coefficient of static friction
0.75, then h is (𝑔𝑔 = 10𝑚𝑚𝑠𝑠 −2 )
between the block and the plane is:
(a) 0.20 𝑚𝑚
(b) 0.45 𝑚𝑚
√3
(c) 0.60 𝑚𝑚 (a)
2
(d) 0.80 𝑚𝑚
√3
(b)
4
1
(c)
Q2. Two blocks 𝐴𝐴 and 𝐵𝐵 masses 𝑚𝑚𝐴𝐴 = 1 𝑘𝑘𝑘𝑘 2
and 𝑚𝑚𝐵𝐵 = 3 𝑘𝑘𝑘𝑘 are kept on the table as 2
shown in the figure. The coefficient of friction (d)
3
between 𝐴𝐴 and 𝐵𝐵 is 0.2 and between 𝐵𝐵 and
the surface of the table is also 0.2. The
maximum force 𝐹𝐹 that can be applied on 𝐵𝐵
horizontally, so that the block 𝐴𝐴 does not
slide over the block 𝐵𝐵 is:
(a) 8 𝑁𝑁
(b) 16 𝑁𝑁
(c) 40 𝑁𝑁
(d) 12 𝑁𝑁
Waves 2
TODAY’S DPP: Q7. At nodes in stationary waves
(a) change in pressure and density are
maximum
Q4. For a certain organ pipe, three
(b) change in pressure and density are
successive resonance frequencies are
minimum
observed at 425, 595 and 765 𝐻𝐻𝐻𝐻. The speed
of sound in air is 340 𝑚𝑚𝑠𝑠 −1. The pipe is a
(c) strain is zero
(a) closed pipe of length 1 m (d) energy is maximum
(b) closed pipe of length 2 m
(c) open pipe of length 1 m
Q8. A resonating column has resonant
(d) open pipe of length 2 m frequencies as 100 𝐻𝐻𝐻𝐻, 300 𝐻𝐻𝐻𝐻, 500 𝐻𝐻𝐻𝐻.
Then, it may
(a) an open pipe
Q5. The fundamental frequency of a
vibrating organ pipe is 100 𝐻𝐻𝐻𝐻. Select the (b) a pipe closed at both ends
wrong alternative.
(c) pipe closed at one end
(a) The first overtone is 200 Hz
(b) The first overtone may be 400 Hz (d) Data insufficient
(c) The first overtone may be 300 Hz
(d) None of the above Q9. An organ pipe 𝑃𝑃1 is closed at one end
and vibrating in its first overtone and another
pipe 𝑃𝑃2 opened at both ends vibrating in its
Q6. A closed organ pipe and an open organ third overtone are in resonance with a given
pipe of same length produce 2 beats when tuning fork. Then, the ratio of lengths 𝑃𝑃1 and
they are set into vibrations simultaneously in 𝑃𝑃2 is
their fundamental mode. The length of open
organ pipe is now halved and of closed organ (a) 1/3
pipe is doubled. The number of beats
produced will be (b) 2/3
(a) 8 (c) 8/3
(b) 7
(d) 3/8
(c) 4
(d) 2
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Waves 3
Q10. The 3𝑟𝑟𝑟𝑟 overtone of a closed organ Q13. When two waves of almost equal
pipe is equal to the 2𝑛𝑛𝑛𝑛 harmonic of an open frequencies 𝜈𝜈1 and 𝜈𝜈2 reach at a point
organ pipe. Then the ratio of their lengths is simultaneously, the time interval between
equal to successive maxima is
(a) 7/4 (a) 𝜈𝜈1 + 𝜈𝜈2
(b) 3/5 (b) 𝜈𝜈1 − 𝜈𝜈2
(c) 3/2 1
(c)
𝜈𝜈1 +𝜈𝜈2
(d) 7/6
1
(d)
𝜈𝜈1 −𝜈𝜈2
Q11. Which of the following phenomenon is
used by the musicians to tune their musical
instruments?
(a) Interference Q14. Two tuning forks, 𝐴𝐴 and 𝐵𝐵, produce
notes of frequencies 258 𝐻𝐻𝐻𝐻 and 262 𝐻𝐻𝐻𝐻. An
(b) Diffraction unknown note sounded with 𝐴𝐴 produces
certain beats. When the same note is
(c) Beats sounded with 𝐵𝐵, the beat frequency gets
doubled. The unknown frequency is
(d) Polarization
(a) 250 Hz
(b) 252 Hz
Q12. The phenomenon of beats can take
place (c) 254 Hz
(a) for longitudinal waves only (d) 256 Hz
(b) for transverse wave only
(c) for sound waves only
(d) for both longitudinal and transverse
waves
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Waves 4
Q15. A tuning fork 𝐴𝐴 of frequency 512 𝐻𝐻𝐻𝐻 Q17. A tuning fork whose frequency as given
produces 5 beats per second when sounded by manufacturer is 512 Hz is being tested
with another tuning fork 𝐵𝐵 of unknown with an accurate oscillator. it is found that the
frequency. If 𝐵𝐵 is loaded with wax the fork produces a beat of 2 Hz when oscillator
number of beats is again 5 per second. The reads 514 Hz but produces a beat of 6 Hz
frequency of the tuning fork 𝐵𝐵 before it was when oscillator reads 510 Hz. The actual
loaded is frequency of fork is
(a) 502 Hz (a) 508 Hz
(b) 507 Hz (b) 512 Hz
(c) 517 Hz (c) 516 Hz
(d) 522 Hz (d) 518 Hz
Q16. Beats are produced by two waves Q18. Two tuning forks have frequencies 450
given by 𝑦𝑦1 = 𝑎𝑎 𝑠𝑠𝑠𝑠𝑠𝑠2000𝜋𝜋𝜋𝜋 and 𝑦𝑦2 = Hz and 454 Hz respectively. On sounding
𝑎𝑎 𝑠𝑠𝑠𝑠𝑠𝑠2008 𝑛𝑛𝑛𝑛 . The number of beats heard these forks together, the time interval
per second is between successive maximum intensities
will be
(a) Zero
(a) 1/4 sec
(b) One
(b) 1/2 sec
(c) Four
(c) 1 sec
(d) Eight
(d) 2 sec
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Waves 5
ANSWERS
1. a 7. b 13. d
2. b 8. c 14. c
3. a 9. d 15. c
4. a 10. a 16. c
5. b 11. c 17. c
6. b 12. d 18. a
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