A boat moves downstream at 10 m s⁻¹ in a river flowing at 2 m s⁻¹. A sound transmitter attached to the boat is lowered into the river and emits wavelength 14.45 mm. (a) Find the frequency detected by a stationary receiver downstream. (b) The transmitter and receiver are then raised into air; wind blows at 5 m s⁻¹ opposite to the river flow. Find the detected frequency. Take water: ρ = 10³ kg m⁻³, B = 2.088 × 10⁹ Pa. For air at 20°C take R = 8.31 J mol⁻¹ K⁻¹, molar mass = 28.8 × 10⁻³ kg mol⁻¹, and Cₚ/Cᵥ = 1.4.
Physics · Wave Motion
A boat moves downstream at 10 m s⁻¹ in a river flowing at 2 m s⁻¹. A sound transmitter attached to the boat is lowered into the river and emits wavelength 14.45 mm. (a) Find the frequency detected by a stationary receiver downstream. (b) The transmitter and receiver are then raised into air; wind blows at 5 m s⁻¹ opposite to the river flow. Find the detected frequency. Take water: ρ = 10³ kg m⁻³, B = 2.088 × 10⁹ Pa. For air at 20°C take R = 8.31 J mol⁻¹ K⁻¹, molar mass = 28.8 × 10⁻³ kg mol⁻¹, and Cₚ/Cᵥ = 1.4.
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