A 100-kg object is moving at 20 m/s when a force brings the object to rest 3 points
in 1.5 seconds. If the same object moving at the same initial speed was
brought to rest in 3.0 seconds, then the required force would be
times the original value. Fill in the blank with the factor that would make
the statement correct. Then explain, in detail, how you picked your answer.

Atrain is traveling at 30.0 m/s relative to the ground in still air. the frequency of the note emitted by the train whistle is 262 hz. the speed of sound in air should be taken as 344 m/s. what frequency (f approach) is heard by a passenger on a train moving at a speed of 18.0 m/s relative to the ground in a direction opposite to the first train and approaching it? what frequency (f recede) is heard by a passenger on a train moving at a speed of 18.0 m/s relative to the ground in a direction opposite to the first train and receding from it?