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# vectors question m1 helpp ! watch

1. A ship P initially has position vector (-3i-2j)km relative to a port at O and moves with velocity (2i+4j)kmh
a. What is its position vector after i.) 2 hours ii.) t hours

b.) When is the ship due west of the port ?

Now I understand the first part but all they have said for b is its due west of the port when j = 0 an figured t=1/2 I dont understand how they have come to this conclusion what j has to do with being west overall im just confused if someone could please explain b this would be so helpful ! thankss
A ship P initially has position vector (-3i-2j)km relative to a port at O and moves with velocity (2i+4j)kmh
a. What is its position vector after i.) 2 hours ii.) t hours

b.) When is the ship due west of the port ?

Now I understand the first part but all they have said for b is its due west of the port when j = 0 an figured t=1/2 I dont understand how they have come to this conclusion what j has to do with being west overall im just confused if someone could please explain b this would be so helpful ! thankss
when the ship is due east or west the J components are 0

when the ship is due north or south the I components are 0

u said u figured T= 0.5, if u still dont understand quote me

the ship is due west of the port 0.5 hours are starting, so u add 0.5 hours to the time the ships starts ( usually at noon, midday etc )
3. (Original post by Vorsah)
when the ship is due east or west the J components are 0

when the ship is due north or south the I components are 0

u said u figured T= 0.5, if u still dont understand quote me

the ship is due west of the port 0.5 hours are starting, so u add 0.5 hours to the time the ships starts ( usually at noon, midday etc )
ok yeah thanks but i dont understand why its due north or south when i components are zero if you could please explain and give example sorry still confused :s
ok yeah thanks but i dont understand why its due north or south when i components are zero if you could please explain and give example sorry still confused :s
Think of the port as the origin of a set of axes. If you think about it, you have to be on the vertical axis to be north of O, and the coordinates will be (0, something). Similarly, to be south, you have to have coordinates
(0, -something). This is because you go "zero across, something up/down". Get it?

If in doubt, draw a set of x-y axes, mark on the origin and notice that you have to be above/below it to be north/south.

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Updated: March 20, 2013
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