Two trains on separate tracks move toward each other. Train A has a speed of 116 km/h. Train B has a speed of 67.0 km/h. Train B blows its hom emitting a frequency of 500 Hz. (THIS IS AN EXAM QUESTION.) 21.) Find the frequency heard by the engineer on Train A. Give answer in Hz. (A) 425 (B) 578 (C) 431 (D) 415 (E) 365 22.) If the train raises the volume of its horn by a factor of 2.5, how many decibels does it increase by? Give an answer in dB. (A) 4.6 (C) 4.2 (D) 2.7 (E) 4.0 23.) If an observer hears the train hom and moves to a location that is three times as far away, by what factor does the intensity of sound change? (A) 1/9 (B) 1/6 (C) 1/4 (D) 1/16 (E) 1/25 24.) If the temperature of the air drops by half, by what factor would the speed of the sound in air change by? (A) 4 (B) 1/4 (C) 2 (D) 2 (E)/2 (B) 5.9 25.) Another observer is standing at the train station (Point D) as Train B passes by at a distance of d= 7,000 m away. (See the diagram.) At that instant, what is the minimum distance, L, that Train A and Train B could be separated by in order to have destructive interference at the location of the observer? Assume Train A blows also blows its hom emitting a frequency of 500 Hz. Give an answer in meters. (C) 69.3 (A) 51.6 (D) 87.9 (B) 98.7 (E) 101 -L B d 3