#9 help plssssssssss

A train whistle is heard at 300 Hz as the train approaches town. The train cuts its speed in half as it nears the station, and t

spin [16.1K]

Answer:

The speed of the train before and after slowing down is 22.12 m/s and 11.06 m/s, respectively.

Explanation:

We can calculate the speed of the train using the Doppler equation:

$f = f_{0}\frac{v + v_{o}}{v - v_{s}}$

Where:

f₀: is the emitted frequency

f: is the frequency heard by the observer

v: is the speed of the sound = 343 m/s

$v_{o}$ : is the speed of the observer = 0 (it is heard in the town)

$v_{s}$ : is the speed of the source =?

The frequency of the train before slowing down is given by:

$f_{b} = f_{0}\frac{v}{v - v_{s_{b}}}$ (1)

Now, the frequency of the train after slowing down is:

$f_{a} = f_{0}\frac{v}{v - v_{s_{a}}}$ (2)

Dividing equation (1) by (2) we have:

$\frac{f_{b}}{f_{a}} = \frac{f_{0}\frac{v}{v - v_{s_{b}}}}{f_{0}\frac{v}{v - v_{s_{a}}}}$

$\frac{f_{b}}{f_{a}} = \frac{v - v_{s_{a}}}{v - v_{s_{b}}}$ (3)

Also, we know that the speed of the train when it is slowing down is half the initial speed so:

$v_{s_{b}} = 2v_{s_{a}}$ (4)

Now, by entering equation (4) into (3) we have:

$\frac{f_{b}}{f_{a}} = \frac{v - v_{s_{a}}}{v - 2v_{s_{a}}}$

$\frac{300 Hz}{290 Hz} = \frac{343 m/s - v_{s_{a}}}{343 m/s - 2v_{s_{a}}}$

By solving the above equation for $v_{s_{a}}$ we can find the speed of the train after slowing down:

$v_{s_{a}} = 11.06 m/s$

Finally, the speed of the train before slowing down is:

$v_{s_{b}} = 11.06 m/s*2 = 22.12 m/s$

Therefore, the speed of the train before and after slowing down is 22.12 m/s and 11.06 m/s, respectively.

I hope it helps you!

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3 years ago

.. Solve: 91

Elan Coil [88]

Explanation:

bro I have no idea fam......

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Steve is planning his annual Spring Break road trip. He pulls out his map and draws out his route to visit the five locations th

Aleksandr [31]

Answer:

His average speed.

Explanation:

Average speed = Total distance travelled / total time .

In the given case odometer measures total distance travelled . Dividing it by time will give average speed .

Average velocity can not be the answer as it is measured by dividing displacement by time . Displacement here is zero because initial and final point are same . Instantaneous velocity is given by the speedometer . It keeps on changing all the time . It is actually speed at a particular point of time . It can not be average velocity or speed .

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3 years ago

High exposure to which type of electromagnetic radiation can cause genetic

melamori03 [73]

The answer is microwaves

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3 years ago

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Energy captured during the ""photo"" part of photosynthesis is stored in _____ during the ""synthesis"" part of the process.

andre [41]

Energy captured during the ""photo"" part of photosynthesis is stored in <u>covalent bond</u> during the ""synthesis"" part of the process.

<u>Explanation:</u>

When carbon dioxide, water and sunlight are combindly processed by Plants, algae and a set of bacteria called cyanobacteria to become photoautotrophs, then the process goes is named as Photosynthesis. It generates oxygen, Glyceraldehyde-3-phosphate (G3P), common high-energy carbohydrate molecules which result into glucose, sucrose or other sugar molecules which comprises covalent energy-saving bonds.

Thus the species breakdown these molecules to exhibit energy for cellular functioning. In light-dependent processes, chlorophyll absorbs the radiation from the sunlight and converts it into chemical energy in the form of electron carrier derivatives such as ATP and NADPH. Carbohydrate molecules are constructed from carbon dioxide in light-independent processes i.e in the Calvin cycle, using the chemical energy obtained throughout the light-dependent processes.

5 0

4 years ago