Objects A and B are at the origin. If object A moves to #(-7 ,5 )# and object B moves to #(-5 ,-2 )# over #2 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
Dec 3, 2017

Answer:

#vecv_{Ag} =(-7/2, 5/2);\qquad vecv_{Bg} = (-5/2, -1);#

#vecv_{BA} = vecv_{Bg} + vecv_{gA} = vecv_{Bg} - vecv_{Ag} = (1, 7/2);#

Explanation:

Velocity of A relative to ground:
#vecv_{Ag} = (\Deltavecr_A)/(\Deltat) = ((-7,5)-(0,0))/2=(-7/2, 5/2);#

Velocity of B relative to ground:
#vecv_{Bg} = (\Deltavecr_B)/(\Deltat) = ((-5-2)- (0,0))/2=(-5/2, -1);#

Velocity of B relative to A:
#vecv_{BA} = vecv_{Bg} + vecv_{gA} = vecv_{Bg} - vecv_{Ag};#

#vecv_{BA} = (-5/2, -1)-(-7/2,5/2) = (1, 7/2);#