Homework Help: physic

Posted by tyler on Tuesday, August 21, 2012 at 9:35pm.

In order to qualify for the finals in an race, a runner must achieve an average speed of 5.24 m/s for the entire mile race. If she runs at a constant speed of 4.63 m/s for the first half of the 1609 meter race, what constant speed must she maintain for the second half of the race in order to qualify?

physic - Elena, Wednesday, August 22, 2012 at 5:38am
v=s/t=s/(t1+t2) = s/[(s/2•v1)+(s/2•v2)] =2•v1•v2/(v1+v2)
v2=v•v1/(2•v1-v)=5.24•4.63/(2•4.63-5.24) = 6.04 m/s

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