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Explain how i and j notation works please? watch

1. As stated in question
2. vector notation? i means change in x, j means change in y.
3. (Original post by thefatone)
As stated in question
Do you mean like in vectors?
i=x, j=y
It's just different names for things.
4. What are you talking about? Unit vectors, matrix indexing, summation indexing etc.?
5. (Original post by rayquaza17)
Do you mean like in vectors?
i=x, j=y
It's just different names for things.
yea sorta these sort of question i don't know how to answer it doesn't make any sense to me
A particle P moves in a straight line with constant velocity. Initially P is at thepoint A with position vector (2i − j) m relative to a fixed origin O, and 2 s later itis at the point B with position vector (6i + j) m.

(a) Find the velocity of P.
(b) Find, in degrees to one decimal place, the size of the angle between thedirection of motion of P and the vector i.

Three seconds after it passes B the particle P reaches the point C.
(c) Find, in m to one decimal place, the distance OC.
6. (Original post by thefatone)
yea sorta these sort of question i don't know how to answer it doesn't make any sense to me
A particle P moves in a straight line with constant velocity. Initially P is at thepoint A with position vector (2i − j) m relative to a fixed origin O, and 2 s later itis at the point B with position vector (6i + j) m.

(a) Find the velocity of P.
(b) Find, in degrees to one decimal place, the size of the angle between thedirection of motion of P and the vector i.

Three seconds after it passes B the particle P reaches the point C.
(c) Find, in m to one decimal place, the distance OC.
i = 1 in x direction, j = 1 in y direction. So you can find out how far it has travelled in that time by the differences in the points.
7. (Original post by Vikingninja)
i = 1 in x direction, j = 1 in y direction. So you can find out how far it has travelled in that time by the differences in the points.
hold on a sec i don't even know how to do part a) yet xD
8. (Original post by thefatone)
hold on a sec i don't even know how to do part a) yet xD
That is for a.
9. is the unit vector in the positive x direction.
is the unit vector in the positive y direction.
is the unit vector in the positive z direction.
Unit means the length of the vector is 1.

So a point has a position vector .
10. (Original post by morgan8002)
is the unit vector in the positive x direction.
is the unit vector in the positive y direction.
is the unit vector in the positive z direction.
Unit means the length of the vector is 1.

So a point has a position vector .
woah buddy this is only M1
11. (Original post by Vikingninja)
That is for a.
well i have no idea where to start or what to do
12. Basically it's like moving 5m/s in the diagonal direction is the same as moving 4m horizontal and 3m vertical if you know what I mean. So instead of saying 5m the split it into the horizontal and vertical components and say (4i + 3j)m/s instead of 5m/s. The I and j are just names for horizontal and verticals components.
13. (Original post by thefatone)
woah buddy this is only M1
Don't worry about then. I don't think I've ever seen used in M1.
14. (Original post by thefatone)
well i have no idea where to start or what to do
Velocity is the distance divided by time. With the vectors work out the distance between them. They form a right angled triangle with the x and y axis so use this to find the distance which is the hypotenuse.
15. (Original post by Vikingninja)
Velocity is the distance divided by time. With the vectors work out the distance between them. They form a right angled triangle with the x and y axis so use this to find the distance which is the hypotenuse.
i got root 5 ms^-1 is that right?
16. (Original post by morgan8002)
is the unit vector in the positive x direction.
is the unit vector in the positive y direction.
is the unit vector in the positive z direction.
Unit means the length of the vector is 1.

So a point has a position vector .
Are the hats really necessary? I thought that was already defacto the unit vector in the positive x direction, etc...
17. (Original post by thefatone)
i got root 5 ms^-1 is that right?
I got it as well.
18. (Original post by Zacken)
Are the hats really necessary? I thought that was already defacto the unit vector in the positive x direction, etc...
They're not really necessary. I just prefer that form. Everything's explicit.
19. (Original post by Zacken)
Are the hats really necessary? I thought that was already defacto the unit vector in the positive x direction, etc...
The hats are for in the direction. Without the hats is for the position as in for a location.
20. (Original post by morgan8002)
Not really. I just prefer that form. Everything's explicit.
Ah, okay. Fair enough; thanks for clarifying.

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