Problem 271//Sound training
In the third installment of the Back to the Future trilogy, Doc Brown engineers a steam locomotive capable of time travel. Inspired by the design, you’ve rigged an antique locomotive going from Absecon, N.J. to Okeechobee, Fla. to try your own hand at turning back the clock.
Your train is travelling at a constant speed and approaching a tunnel, lying straight ahead. You sound a blast of the whistle and hear the return echo six seconds later. At that same instant, you sound the whistle again and hear the echo from this blast five seconds later. If the speed of sound is 1,100 ft/s, how fast is your train going? Is that fast enough to reach the 88 mph required by your flux capacitor to break the time barrier?
