The velocity of propagation of a transverse wave on a stretched string is given by
$$v = \sqrt {\left( {\frac{T}{\mu }} \right)} $$
where $$T$$ is tension in the string and $$\mu $$ is linear density of the string i.e. mass per unit length of the string.
$$\eqalign{
& {\text{Here,}}\,\,\mu = \frac{{0.035}}{{5.5}}kg/m \cr
& T = 77\,N \cr
& \therefore v = \sqrt {\frac{{77 \times 5.5}}{{0.035}}} \cr
& = 110\,m/s \cr} $$
2.
Two cars moving in opposite directions approach each other with speed of $$22\,m/s$$ and $$16.5\,m/s$$ respectively. The driver of the first car blows a horn having a frequency $$400\,Hz.$$ The frequency heard by the driver of the second car is [velocity of sound $$340\,m/s$$ ]
When both source and observer are moving towards each other, apparent frequency is given by
$${f_a} = {f_0}\left( {\frac{{v + {v_0}}}{{v - {v_s}}}} \right)$$
where,
$${{f_0}} = $$ original frequency of source
$${{v_s}} = $$ speed of source
$${{v_0}} = $$ speed of observer
$$v = $$ speed of sound
Frequency of the horn,
$${f_0} = 400\,Hz$$
Speed of observer in the second car,
$${v_0} = 16.5\,m/s$$
Speed of source,
$$\eqalign{
& {v_s} = {\text{speed of first car}} \cr
& = 22\,m/s \cr} $$
Frequency heard by the driver in the second car
$$\eqalign{
& {f_a} = {f_0}\left( {\frac{{v + {v_0}}}{{v - {v_s}}}} \right) = 400\left( {\frac{{340 + 16.5}}{{340 - 22}}} \right) \cr
& = 448\,Hz \cr} $$
3.
A transverse wave is represented by $$y = A\sin \left( {\omega t - kx} \right).$$ For what value of the wavelength is the wave velocity equal to the maximum particle velocity?
4.
Three sound waves of equal amplitudes have frequencies $$\left( {\nu - 1} \right),\nu ,\left( {\nu + 1} \right).$$ They superpose to give beats. The number of beats produced per second will be:
Maximum number of beats $$ = \left( {\nu + 1} \right) - \left( {\nu - 1} \right) = 2$$
5.
A sonometer wire of length $$1.5\,m$$ is made of steel. The tension in it produces an elastic strain of 1%. What is the fundamental frequency of steel if density and elasticity of steel are $$7.7 \times {10^3}kg/{m^3}$$ and $$2.2 \times {10^{11}}N/{m^2}$$ respectively?
6.
A wave travelling in the positive $$x$$-direction having displacement along $$y$$ -direction as $$1\,m,$$ wavelength $$2\pi \,m$$ and frequency of $$\frac{1}{\pi }Hz$$ is represented by
A.
$$y = \sin \left( {x - 2t} \right)$$
B.
$$y = \sin \left( {2\pi x - 2\pi t} \right)$$
C.
$$y = \sin \left( {10\pi x - 20\pi t} \right)$$
D.
$$y = \sin \left( {2\,\pi x + 2\,\pi t} \right)$$
7.
A vibrating string of certain length $$\ell $$ under a tension $$T$$ resonates with a mode corresponding to the first overtone (third harmonic) of an air column of length $$75\,cm$$ inside a tube closed at one end. The string also generates 4 beats per second when excited along with a tuning fork of frequency $$n.$$ Now when the tension of the string is slightly increased the number of beats reduces 2 per second. Assuming the velocity of sound in air to be $$340\,m/s,$$ the frequency $$n$$ of the tuning fork in $$Hz$$ is
The frequency $$\left( \nu \right)$$ produced by the air column is given by
$$\eqalign{
& \lambda \times \nu = \nu \cr
& \Rightarrow \,\,\nu = \frac{\nu }{\lambda } \cr
& {\text{Also, }}\frac{{3\lambda }}{4} = \ell = 75cm = 0.75m \cr
& \therefore \,\,\lambda = \frac{{4 \times 0.75}}{3} \cr
& \Rightarrow \,\nu = \frac{{340 \times 3}}{{4 \times 0.75}} \cr
& = 340Hz \cr} $$
$$\therefore $$ The frequency of vibrating string = 340. Since this string produces 4 beats/sec with a tuning fork of frequency $$n$$ therefore $$n = 340 + 4$$ or $$n = 340 - 4.$$ With increase in tension, the frequency produced by string increases. As the beats/sec decreases therefore $$n = 340 + 4 = 344\,Hz.$$
8.
Two travelling waves $${y_1} = A\sin \left[ {k\left( {x - ct} \right)} \right]$$ and $${y_2} = A\sin \left[ {k\left( {x + ct} \right)} \right]$$ are superimposed on string. The distance between adjacent nodes is
9.
If there are six loops for $$1\,m$$ length in transverse mode of Meldeās experiment., the no. of loops in longitudinal mode under otherwise identical conditions would be
No. of loops in longitudinal mode $$ = \frac{6}{2} = 3$$
10.
While measuring the speed of sound by performing a resonance column experiment, a student gets the first resonance condition at a column length of $$18\,cm$$ during winter. Repeating the same experiment during summer, she measures the column length to be $$x\,cm$$ for the second
resonance. Then