Russia Vs ISIS!

Classical Mechanics Level 5

Yesterday I was observing a Russian air jet which was flying above Jableh's airspace and heading to bomb the ISIS, It was like 1 km high, I have the "STD" which is a voice tracking device "it allows me to know the location of any sound source by tracking it by its sound waves!.

My device showed that the angle between the aircraft and the horizontal (45.32D) , and I managed to measure the angle and was 37.40D.

What is the time required aircraft to get to the nearest ISIS site?

Details And Assumptions:

-Neglect the relativistic effects.

-Assume that the sound wave speed is 343.24m/s.

-The Russian aircraft is flying in a straight line and towards me.

-The Russian air craft was flying on the same high level.

-The aircraft sticks to the same velocity.

-The nearest ISIS site is 40km away from Jableh!

-Report you answer in minutes up to two decimal places.

The answer is 10.02.

1 solution

Jafar Badour
Oct 8, 2015

the distance between the place of the aircraft and its place according to the sound is $\delta$

$\delta =h(cot(37.4)-cot(45.32))$

$\delta =319.053m$

now the time which sound required to get to the observer $\tau =r/v_sound$

$\tau =\frac{h}{sin(37.4)v_s }=4.796s$

so the speed of the aircraft is $v=\frac{\delta}{\tau}=66.51m/s$

the minimum time to Russian Aircraft to reach the nearest ISIS site is:

$\tau_A=\frac{\delta_2}{v}=\frac{40000}{66.51}=10.02minute$

The question is not stated properly.

Abhijith Asokan - 5 years, 8 months ago

the question itself isnt hard at all. It's how the problem stated that makes it hazy & hard. In fact, with basic geometry, you can measure the initial angle without recording the sound. On the other hand, it is absurd for a bombing jet to fly at a speed of ~66m/s while others fly at super sonic speed.

Hieu Pham - 5 years, 3 months ago

@jafar badour What does mean $D$ in the problem?

. . - 2 months, 2 weeks ago

Russia Vs ISIS!

The answer is 10.02.

1 solution

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