Frequency heard, need someone to check

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AI Thread Summary
The problem involves calculating the frequency heard by a passenger on a train moving towards a whistle from another train. The formula used accounts for both the listener's and the source's velocities relative to the speed of sound. After applying the values, a frequency of 288 Hz was calculated. This result aligns with the expectation that the listener perceives a higher frequency due to the approaching source. Confirmation of the calculation's accuracy is sought.
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Homework Statement



A train is traveling 30 m/s in still air. The frequency of the train whistle is f = 250 Hz. What frequency is head by a passenger on a train moving in the opposite direction at 18 m/s and approaching the first train? The velocity of sound in air is 344 m/s.

Homework Equations



F = [(1(+/-) (Velocity listener)/velocity sound) / (1(+/-) (Velocity source)/velocity sound)] *frequency

The Attempt at a Solution



Since the listener is moving towards the source and the source is moving towards the listener the forumula becomes

F = [(1+(Velocity listener)/velocity sound) / (1 - (Velocity source)/velocity sound)] *frequency

After plugging in the numbers i got 288Hz, is that correct?

it makes sense because the listener would hear a higher frequency b/c the source is moving towards the listener

thanks
 
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so, is it right?
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
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