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# Stuck on another vectors question about intercepting boats Watch

1. A small boat S, drifting in the sea, is modelled as a particle moving in a straight line at constant speed. When first sighted at 0900, S is at a point with position vector (-2i-4j)km relative to a fixed origin O, where i and j are unit vectors due east and due north respectively. At 0940, S is at the point with position vector (4i-6j)km. At time t hours after 0900, S is at the point with position vector skm.

a) Calculate the bearing on which S is drifting. (108)
b) Find an expression for s in terms of t. (-2+9t)i + (-4-3t)j
at 1100 a motor boat M leaves O and travels with constant velocity (pi+qj)kmh-1
c) Given that M intercepts S at 1130, calculate the value of p and the value of q

I've done parts a and b but need some guidance on c, don't even know where to start.
2. Anyone?
3. (Original post by Nida123)
Anyone?
Perhaps so, but not in the time you want.

Have you got any info written down where you have set the i and j components equal?
4. I don't get how you would set the I and I components equal because I haven't got a position vector for m :/ I know the position vector of m would equal the position vector is s at 1130 but I don't know how I would do that, does it involve using the equation from b. I'm really confused
5. (Original post by Nida123)
I don't get how you would set the I and I components equal because I haven't got a position vector for m :/ I know the position vector of m would equal the position vector is s at 1130 but I don't know how I would do that, does it involve using the equation from b. I'm really confused
Use part (b) to work out where S is at 11:30. This will be a vector like mi + nj where m and n are just numbers.

Using the speed vector they've given you for M, work out where M will be at 11:30 (be careful, because M's "time" starts at 11:00, not 09:00)

Set the 2 position vectors equal to each other, and equate the i and j components.

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Updated: April 9, 2013
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