A boat is travelling in a river with a speed 10 m/s along the stream flowing with a speed 2 m/s. From this boat, a sound transmitter is lowered into the river through a rigid support. The wavelength of the sound emitted from the transmitter inside the water is 14:45 mm. Assume that attenuation of sound in water and air is negligible.(a) What will be the frequency detected by a receiver kept inside the river downstream?(b)The transmitter and the receiver are now pulled up into air. The air is blowing with a speed 5 m/s in the direction opposite the river stream. Determine the frequency of the sound detected by the air receiver.(Temperature of the air and water = 20° C; Density of river water = 103 kg/m3 ; Bulks modulus of the water = 2.088 x 109 Pa ; Gas constant R = 8.31 J/mol – K ; Mean molecular mass of air = 28.8 x 10-3 kg/mol ; Cp Cv for air = 1.4)

Simran Bhatia , 10 Years ago

Grade 11