Question1
Train Spring
A number of train stations have large horizontal springs at the ends of the tracks. These are safety devices to stop train so that it will not go plowing through the station in the event an engineer is too busy texting. You would like to know how fast a train might be going and still be safely stopped by spring. It looks like the spring is about three meters long. Maximum safe acceleration for passengers while stopping is about half of g. You know from years of reading books about trains that a typical train has a mass of 5E5 kg.
Question2
You are standing 2.5 {rm m} directly in front of one of the two loudspeakers. They are 3.0 {rm m} apart and both are playing a 686 {rm Hz} tone in phase. As you begin to walk directly away from speaker, at what distances from the speaker do you hear the minimum sound intensity? The room temperature is 20 ^circ {rm C}.