i dont even know where to start with this problem! pleasehelp!! Two children who

Question

i dont even know where to start with this problem! pleasehelp!! Two children who are bored while waiting for their flight atthe airport decide to race from one end of the 20m long movingsidewalk to the other and back. phillippe runs on the sidewalk at2.0m/s (relative to the sidewalk). renee runs on the floor at2.0m/s. the side wald moves at 1.5m/s relative to the floor. bothmake the turn instantly with no loss of speed. part A: who wins the race? phillippe or renee part B: by how much time does the winner win? i dont even know where to start with this problem! pleasehelp!! Two children who are bored while waiting for their flight atthe airport decide to race from one end of the 20m long movingsidewalk to the other and back. phillippe runs on the sidewalk at2.0m/s (relative to the sidewalk). renee runs on the floor at2.0m/s. the side wald moves at 1.5m/s relative to the floor. bothmake the turn instantly with no loss of speed. part A: who wins the race? phillippe or renee part B: by how much time does the winner win?

Explanation / Answer

Phillippe is running at 2.0m/s relative to the sidewalk. Renee is running at 2.0m/s relative to the floor. The sidewalk is moving at 1.5m/s relative to the floor. Those airport moving sidewalks go in one direction so one wayPhillipe wille moving 2.0m/s+1.5m/s relative to the floor and theother way he will be moving 2.0m/s-1.5m/s relative to the floor (itdoesn't matter which way he is moving slower or faster since it'sequal distance/no accelerations). Let's say he moves slower on the way there. He will be moving2.0m/s-1.5m/s = 0.5m/s relative to the floor. It will takehim: 20m/(0.5m/s) = 40 seconds to get there. To get back he will be moving 2.0m/s+1.5m/s = 3.5m/s relative tothe floor. It will take him: 20m/(3.5m/s) = approx. 5.71seconds. So his total time will be about 45.71 seconds. Renee is moving 2.0m/s relative to the floor both times so it willtake her 40m/2.0m/s for the entire trip which is 20 seconds. So shewill win and by about 25.71 seconds.

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