Question

A submarine can detect an approaching enemy submarine using sonar. If a stationary submerged submarine emits a 100kHz tone and receives a tone Doppler shifted by 200Hz, calculate the speed of the enemy submarine if the speed of sound in salt water is 1,482m/s. Note: Because the echo is off of a moving object, the moving object amplifies the Doppler effect by a factor of 2! Therefore, the speed must be cut in half. A. 1.0m/s B. 1.5m/s C.2.2m/s OD.3.3m/s E. 4.4m/s

Answer 1

Answer:

B ) 1.5 m/s

Explanation:

For the apparent frequency reflected by enemy submarine , the Doppler effect formula is

F = F₀ ( V + v) / (V - v)

F anf F₀ are real and apparent frequency , V and v are velocity of sound and velocity of enemy submarine respectively.

ΔF / F₀ = $\frac{2\times v}{V -v}$

Put ΔF = 200;  F₀ = 100000 and  V = 1482

200 / 100000 = $\frac{2\times v }{1482-v}$

v = 1.5 m s⁻¹ .