Help mathematics oct/nov 2011

[MahnoorDab]

http://www.xtremepapers.com/papers/...S Level/Mathematics (9709)/9709_w11_qp_12.pdf
can anybody please solve Q3 part b for me. The vectors one. Thankyou

 

[fathimaash]

AB=AO+OB
-5 2 -3
AB = -1 + 7 = 6
-2 4 2
mode AB= (-3)2+(6)2+(2)2= 49
Square root of 49= 7
so mode of AB=7
28=7x
4=x
so 4 times of vector AB will give a magnitude of 28
4 * -3 -12
6 = 24
2 8
Hope u understand....

 

[MahnoorDab]

Um the answer should be in terms of i j and k

 

[MahnoorDab]

and i did not get iit :s

 

[fathimaash]

k i will try xplaining to u in words.
First find vector AB by adding AO+OB.
Then find the mode of AB by squaring -3, 6, and 2 and get the square root which is 7 this is the magnitude.
Now the question says to write the vector of magnitude 28. Which is 4 times the vector AB
28 divide by 7 will give 4.
So mutilpy vector AB by 4.... (write in terms of i,j,k) thats ur answer....
HOPE U UNDERSTAND!!!

 

[MindStealth]

To do this question you have to understand first what they're asking for, lets assume the new vector we have to find is named z. They want a vector that has the same direction as AB, that means that means the only difference between AB and z is their magnitude, and that they've given you; 58.
Now first you need to find the the vector AB. This is found by subtraction OA from OB;
OA = OB - OA
Now the next step is to find the direction of AB. Remember the definition of a vector, it shows both the direction and and the magnitude...but we just need its direction. You can find the direction by dividing the vector by its magnitude.
Magnitude of AB = Square root of [(3^2)+(6^2)+(2^2)]
= Square root of 49
= 7
Now find the vector in the direction of AB by diving it by 7.
Now to get z multiply this direction vector by 58, z's magnitude.