The sound was repeated because of the phenomenon of echo. The speed of sound in the metal is 800 m/s.
Echo results from the reflection of sound waves. The reason why a sound may be heard twice owes to the phenomenon of reflection which leads to echo.
To determine the speed of sound in the metal;
Length of metal = 1000 m
Time taken between the two sounds = 2.5 s
Using the formula;
V = 2d/t
V = 2(1000)/2.5
V = 800 m/s
It will be the displacement
Answer
79.8 miles per hours fast is the car going.
Formula
By using the dopplers effect. (When source is approching .)
As given
A car approaches you with its horn blowing.
The observed frequency is 503.7 Hz.
The speed of sound is 1100 ft/s .
The car's horn has a frequency of 450 Hz.
i.e
v = 1100 ft/s
Put in the above formula
Now convert 117.3 ft per second into miles per hours.
117.3 feet per second = 79.8 miles per hours (Approx)
Thus
Therefore the 79.8 miles per hours fast is the car going.
Circuit breaker is a device that is designed to open an overloaded circuit and prevent overheating. The correct option in regards to the given question is option "a". The main purpose of the circuit breaker is to disconnect the defective switch from the circuit as soon as any problem arises. This helps in preventing any kind of major accident. Overheating can result in a big accident and the circuit breaker is the device that senses the overheating and disconnects the switch before any major incident. It is an automated system that acts as a protective devise.