Two trains move towards each other with the same speed. The speed of sound is $340 \;m / s$. If the height of the tone of the whistle of one of them heard on the other changes $9 / 8$ times, then the speed of each train should be ........... $m/sec$
AIPMT 1991, Medium
Download our app for free and get started
Here, $v^{\prime}=\frac{9}{8} v$
Source and observer are moving in opposite direction, therefore, apparent frequency $v^{\prime}=v \times \frac{(v+u)}{(v-u)}$
$\frac{9}{8} v=v \times \frac{340+u}{340-u}$
$\Rightarrow 9 \times 340-9 u=8 \times 340+8 u$
$\Rightarrow 17 u=340 \times 1 \Rightarrow u=\frac{340}{17}=20 m / sec$
Download our appand get started for free
Experience the future of education. Simply download our apps or reach out to us for more information. Let's shape the future of learning together!No signup needed.*
Similar Questions
- 1The two nearest harmonics of a tube closed at one end and open at other end are $220\,\, Hz$ and $260\,\, Hz.$ What is the fundamental frequency of the system .... $Hz$ ?View Solution
- 2The percentage increase in the speed of transverse waves produced in a stretched string if the tension is increased by $4\, \%$, will be ......... $\%$View Solution
- 3A sine wave has an amplitude $A$ and wavelength $\lambda$. Let $V$ be the wave velocity and $v$ be the maximum velocity of a particle in the medium. ThenView Solution
- 4A train $S1$, moving with a uniform velocity of $108 km / h$, approaches another train $S 2$ standing on a platform. An observer $O$ moves with a uniform velocity of $36 km / h$ towards $S 2$, as shown in figure. Both the trains are blowing whistles of same frequency $120 Hz$. When $O$ is $600 m$ away from $S 2$ and distance between $S 1$ and $S 2$ is $800 m$, the number of beats heard by $O$ is. . . . . [Speed of the sound $=330 m / s$ ]View Solution
- 5The frequency changes by $10 \%$ as a sound source approaches a stationary observer with constant speed $V_s$. What would be percentage change in the frequency as the source recedes the observer with same speed $\left(V_s < V\right)$ is ........... $\%$View Solution
- 6The total length of a sonometer wire between fixed ends is $110\, cm$. Two bridges are placed to divide the length of wire in ratio $6 : 3 : 2$. The tension in the wire is $400\, N$ and the mass per unit length is $0.01\, kg/m$ . What is the minimum common frequency with Which three parts can vibrate ........... $Hz$ ?View Solution
- 7View SolutionAt what speed should a source of sound move so that stationary observer finds the apparent frequency equal to half of the original frequency
- 8A car is moving towards a high cliff. The car driver sounds a horn of frequency $f$. The reflected sound heard by the driver has a frequency $2f$. If $v$ be the velocity of sound then the velocity of the car, in the same velocity units, will beView Solution
- 9A second harmonic has to be generated in a string of length $l$ stretched between two rigid supports. The point where the string has to be plucked and touched areView Solution
- 10The mass per unit length of a uniform wire is $0.135\, g / cm$. A transverse wave of the form $y =-0.21 \sin ( x +30 t )$ is produced in it, where $x$ is in meter and $t$ is in second. Then, the expected value of tension in the wire is $x \times 10^{-2} N$. Value of $x$ is . (Round-off to the nearest integer)View Solution