Objects A and B are at the origin. If object A moves to (-2 ,7 ) and object B moves to (6 ,-5 ) over 3 s, what is the relative velocity of object B from the perspective of object A? Assume that all units are denominated in meters.

1 Answer
P dilip_k
Mar 5, 2016

Initially both A and B were at origin O (0,0)
after 3sec A reaches at (-2,7) and B at (6,-5)
So displacement vector of A =-2hati+7hatj m
velocity vector of A, vecV_A=1/3(-2hati+7hatj) m/s
displacement vector of B =6hati-5hatjm
velocity vector of B, vecV_B=1/3(6hati-5hatj) m/s
So the relative velocity of B from the perspective of A is given by
vecV_(BA) =vecV_B-vecV_A =1/3((6+2)hati-(5+7)hatj)
=1/3(8hati-12hatj) m/s
|vecV_(BA)| =1/3sqrt(8^2+12^2)=sqrt208/3=4.81ms^-1

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