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Temka [501]
4 years ago
14

Two trains are traveling on the same track and in the same direction. The first train, which is behind the second train, blows a

horn whose frequency is 269 Hz. The second train detects a frequency of 290 Hz. If the speed of the second train is 13.7 m/s, what is the speed of the first train?
Physics
1 answer:
Andrews [41]4 years ago
5 0

Answer:

37.545 m/s

Explanation:

f' = Actual frequency of horn = 269 Hz

f = Observed frequency of horn = 290 Hz

v = Speed of sound in air = 343 m/s

v_0 = Speed of second train = 13.7 m/s

v_s = Speed of first train

From Doppler effect we have

f=f'\dfrac{v-v_0}{v-v_s}\\\Rightarrow v_s=v-\dfrac{f'}{f}(v-v_0)\\\Rightarrow v_s=343-\dfrac{269}{290}(343-13.7)\\\Rightarrow v_s=37.545\ m/s

The speed of the first train is 37.545 m/s

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Answer:

It will roll up to its initial height from which it rolled from on the first hill

Explanation:

The given information are;

The height from which the ball is rolled = 3 feet[

The equation of the potential energy of the ball as it rolled down the frictionless inclined plane is given by the following equation;

m × g × h₁ = 1/2 × m × v² + 1/2×[2/5× m × r²) × [v/r]

Where;

m = The mass of the ball

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v = The velocity of the ball

r = The radius of the ball

Therefore, all the potential energy, m × g × h, is converted into kinetic energy when the ball reached the ground

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1/2 × m × v² + 1/2×[2/5× m × r²) × [v/r] = m × g × h₂, therefore, we have;

1/2 × m × v² + 1/2×[2/5× m × r²) × [v/r] = m × g × h₁ =  m × g × h₂

Therefore since m × g × h₁ =  m × g × h₂, then h₁ = h₂, the ball rises to the same height it started rolling from on the first hill.

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3 years ago
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laila [671]

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Explanation:

5 0
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bazaltina [42]

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Explanation:

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3 years ago
A police car moving at 36.0 m/s is chasing a speeding motorist traveling at 30.0 m/s. The police car has a siren that emits soun
maxonik [38]

Answer:

The frequency heard by the motorist is 4313.2 Hz.

Explanation:

let f1 be the frequency emited by the police car and f2 be the frequency heard by the motorist, let v1 be the speed of the police car and v2 be the speed of the motorist and v = 343 m/s be the speed of sound.

because the police car is moving towards the motorist at a higher speed, then the motorist will hear a increasing frequency and according to Dopper effect, that frequency is given by:

f1 =  [(v + v2/(v - v1))]×(f2)

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Therefore, the frequency heard by the motorist is 4313.2 Hz.

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