Explanation:
Given that,
Frequency of train horn, f = 218 Hz
Speed of train, 
The speed of sound, V = 344 m/s (say)
The speed of the observed person, 
(a) When the train approaches you, the Doppler's effect gives the frequency as follows :

(b) When the train moves away from you, the Doppler's effect gives the frequency as follows :

Hence, this is the required solution.
The answer is B- 384,400
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Answer:


Explanation:
Density can be found by dividing the mass by the volume.

The mass is 5.28 grams and the volume is 2 cubic centimeters.

Substitute the values into the formula.

Divide.

The density of the unknown substance is 2.64 grams per cubic centimeter.
The density of a diamond is about 3.5 grams per cubic centimeter. Since 2.64 is not equal to 3.5, the unknown substance is not a diamond.
Answer:
Time taken to travel remaining 228 miles = 2.4 hours.
Explanation:
Total distance = 876 miles.
Distance traveled after speed reduction = 228 miles
So, distance traveled before = 876 - 228 =648 miles.
Time taken for this = 6 hours.
Speed before speed reduction = 648/6 = 108 mph.
Speed after speed reduction = 108 - 13 = 95 mph
Time taken to travel remaining 228 miles = 228/95 = 2.4 hours.