Objects A and B are at the origin. If object A moves to (6,7) and object B moves to (6,1) over 3s, what is the relative velocity of object B from the perspective of object A? Assume that all units are denominated in meters.

3 Answers
Apr 29, 2016

83ms1

Explanation:

Relative velocity is a vector quantity. Lets check component wise:

  • x-component:
    Both the bodies have moved to the same vertical line, namely x=6 line. Hence their x-components of the velocities are same.

  • y-component:
    The distance between their final positions is: (7(1))=8 m
    Hence the relative velocity along y-axis is: 83ms1

Hence the relative velocity is 83ms1 along y-axis.

Apr 29, 2016

vA=2,67 m/s

Explanation:

enter image source here
displacement=8 meters

vA=displacementtime

vA=83

vA=2,67 m/s

Apr 29, 2016

In 3s displacement of A from (0.0) to (-6,7) =dA=(6ˆi+7ˆj)m
Velocity of A , VA=dA3=13(6ˆi+7ˆj)ms

In 3s displacement of B from (0.0) to (-6,-1) =dB=(6ˆiˆj)m
Velocity of B, VB=dB3=13(6ˆiˆj)ms
The relative velocity of object B from the perspective of object A
is VBVA=13(6ˆiˆj+6ˆi7ˆj)=83ˆjms
So magnitude of relative velocity is 83ms and it is directed towards negative direction of y-axis i.e. 270o with positive direction of X-axis