Question

Поезд, который движется со скоростью 72 км/ч, издаёт короткие гудки каждые 5 с. На вокзале гудки слышны через промежутки времени, равные 4,7 с. Найти скорость звука.

Answer 1

За время T=5с звук уйдет на расстояние L=U*T

для наблюдателя на земле L=(V+U)*t   t=4,7с
U*T=V*t+U*t

U=V*t/(T-t)=20*4,7/0,3=313,333 м/с

второй способ
L=U*T- расстояние которое пройдет звук за время T=5c
за это время поезд приблизится на расстояние V*T
nтогда t=(L-V*t)/U
U*t=U*T-V*t
U=V*t/(T-t)=20*4,7/0,3=313,333 м/с

Answer 2

Calculation of the Speed of Sound

To find the speed of sound, we can use the information given about the train's speed and the time intervals between the train's horn sounds.

Given: - Speed of the train: 72 km/h - Time interval between horn sounds: 5 seconds - Time interval between hearing the horn sounds at the station: 4.7 seconds

We can use the formula:

Speed of sound = Speed of the train / Time interval difference

Let's calculate the speed of sound using this formula.

Speed of sound = 72 km/h / (5 s - 4.7 s)

To perform the calculation, we need to convert the speed of the train from kilometers per hour to meters per second, as the time interval is given in seconds.

Speed of sound = (72 km/h * 1000 m/km) / (5 s - 4.7 s)

Converting the speed of the train to meters per second:

Speed of sound = (72,000 m/3600 s) / (5 s - 4.7 s)

Simplifying the calculation:

Speed of sound = 20 m/s / 0.3 s

Speed of sound = 66.67 m/s

Therefore, the speed of sound is approximately 66.67 m/s.