Q1. Two trains, each having a speed of 28 km/h, are headed at each other on the similar straight track. A bird that can fly 56 km/h flies off the front of one train, when they are 66 km apart and heads directly for the other train. On reaching the other train it flies straight back to the first train, and so forth. (We have no idea why the bird would behave in this way.) What is the total distance (in km) the bird travels?
Q2. Two loudspeakers in a 20^circ {rm{C}} room emit 690 Hz sound waves along the x-axis.
What is the smallest distance between the speakers for which the interference of the sound waves is destructive?