Posted by jake on Sunday, February 7, 2010 at 8:46pm.
Need help with this short physics question
there is a race betwen person A and person B. They both start at the same time, but B initial position is 10m left of peron A. person A travels 100 meters right in 20 seonds, Person Btravels 112.5 meters right in 15 seconds.
what is the time, postion and, and person B displacement at which Person B catches up with Person A

physics  Anonymous, Sunday, February 7, 2010 at 9:16pm
Consider person A's starting position to be 0.
for person A, d = r * t
d = 100 meters / 20 sec * t
d = 5 meters / sec * t
for person B, d = 10 + (d * t)
d = 10 + (112.5 meters / 15 sec * t)
d = 10 + (7.5 meters / sec * t)
We know the two positions are equal when person A catches person B. So.
5 meters / sec * t = 10 + (7.5 meters / sec * t)
solving that will give you t.
To find the distance, use the simpler of the 2 original equations:
d = 5 meters / sec * t 
physics  jake, Sunday, February 7, 2010 at 10:26pm
i don't get how to find the time