Additional Mathematics Vector Help Centre

[justanotherboy]

So I've gone over these past-papers and examiner reports and I have found out that maximum number of candidates were unable to solve some vector questions properly. Lets change that during the coming session. The Add Math paper is ages away so lets solve some challenging past vector questions that deviate from the textbook method and require creative thinking. Any other challenging and non-textbook oriented questions are also welcome. One such question:

" In this question, i is a unit vector due east and j is a unit vector due north.
At 0900 hours a ship sails from the point P with position vector (2i + 3j) km relative to an origin O.
The ship sails north-east with a speed of 15 2 km h
–1
.
(i) Find, in terms of i and j, the velocity of the ship. [2]
(ii) Show that the ship will be at the point with position vector (24.5i + 25.5j) km at 1030 hours. [1]
(iii) Find, in terms of i, j and t, the position of the ship t hours after leaving P. [2]
At the same time as the ship leaves P, a submarine leaves the point Q with position vector
(47i – 27j) km. The submarine proceeds with a speed of 25 km / h

due north to meet the ship.
(iv) Find, in terms of i and j, the velocity of the ship relative to the submarine. [2]
(v) Find the position vector of the point where the submarine meets the ship."
-Q10, 2008, MJ

 

[rohanbarua]

Hey man!
I did this question and I couldn't figure out why it is 15(root)2 multiplied by (i+j)/(root)2
I did the rest.

Can you tell me any other tips that you know about vector and stuff?

 

[justanotherboy]

Hey. Can you post how you solved the rest of the question please? Yup. I have been able to answer one of the other tough vector questions in the recent papers and will put that up soon.

 

[rohanbarua]

first answer is 15 i + 15 j.
second is basically... (15i + 15j)t + (2i + 3j) where t=1.5
third is (15i + 15j)t + (2i + 3j).

fourth, it will be (15i + 15j) – 25j = 15i – 10j because the speed is vertically downwards (-25j) and the speed of the ship is 15i + 15j and same direction means that it will be minus.
fifth, we have to equate the 2 and using i and j we have to figure out value of t and eventually get the answer as 47i + 48 j

welcome