Speed of a helicopter determined by sonar

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The discussion focuses on calculating the speed of a helicopter using sonar signals. When the helicopter, 700 m from a cliff, transmits a signal and receives it back in 3.4 seconds, the signal travels 1190 m at a speed of 350 m/s. If the helicopter were stationary, the sonar signal would have had to travel 1400 m (700 m to the cliff and 700 m back). Since the signal only traveled 1190 m, the helicopter must have moved closer to the cliff during that time. The key question is determining how much closer the helicopter got and calculating its speed based on that distance.
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Homework Statement



A helicopter flies directly toward a vertical cliff. when the helicopter is 700 m from the cliff face it transmits a sonar signal. it recives the reflected signal 3.4 s later. if the signal travels at a wind speed 350m/s, what is the speed of the helicopter.

The Attempt at a Solution



250*3.4= 1190 m
please help me what i need to do next? i spend 1 hour on it i did n't get answer.
 
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How far did the signal travel in 3.4s?
If the helicopter was stationary it would have to have traveled 2*700=1400m
How much less did it travel?
The helicopter must have traveled that far in 3.4s
 
mgb_phys said:
How far did the signal travel in 3.4s?
If the helicopter was stationary it would have to have traveled 2*700=1400m
How much less did it travel?
The helicopter must have traveled that far in 3.4s

what u mean by 2*700?
 
The distance the sound would have to travel 700m to the cliff and 700m back to the helicopter = 1400m if the helicopter was stationary.
In fact it only goes 3.4*350 = 1190m so the helicopter must have moved how much closer?
 
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