relative velocity question

EmcD123

Two particles A and B have velocities 3i and vj respectively,where v is a constant.

Find the position of B relative to A for all t given that position of B relative to A at t=0 is 10i+5j(in metres)

So ya,I'm really struggling
So far I've found velocity of B relative to A as (-3i+5j)
And multiplied by t to get (-3it+vtj)
Then multiplied by (10i+5j)
In order to get position with respect to t(I think) which is (-3t +10)i +((vt+5)j
I'm totally stuck on what to do next but I'm pretty sure I'm on the right track

dlouth15

Your relative velocity of B is wrong.

A moves at 3i and B moves at vj velocity.

The relative velocity of B relative to a is -3i + vj (i've subtracted the velocity of A from the velocity of

At t=0 the relative position of B is 10i+5j.

So we have the initial relative position and and velocity of B relative to A.

At time t therefore, the relative position will be [the inititial relative position ] + t x [the relative velocity]

= [10i+5j] + t x [-3i + vj]

You can complete it by gathering the i and j terms.

EmcD123

dlouth15 wrote: »

Your relative velocity of B is wrong.

A moves at 3i and B moves at vj velocity.

The relative velocity of B relative to a is -3i + vj (i've subtracted the velocity of A from the velocity of

At t=0 the relative position of B is 10i+5j.

So we have the initial relative position and and velocity of B relative to A.

At time t therefore, the relative position will be [the inititial relative position ] + t x [the relative velocity]

= [10i+5j] + t x [-3i + vj]

You can complete it by gathering the i and j terms.

Thanks. Ya I typed the relative velocity of B relative to A incorrectly.
Thanks I get it now,couldn't figure out the notes from classes