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Explain how i and j notation works please? watch

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    As stated in question
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    vector notation? i means change in x, j means change in y.
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    (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.
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    What are you talking about? Unit vectors, matrix indexing, summation indexing etc.?
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    (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.
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    (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.
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    (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
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    (Original post by thefatone)
    hold on a sec i don't even know how to do part a) yet xD
    That is for a.
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    \hat{i} is the unit vector in the positive x direction.
    \hat{j} is the unit vector in the positive y direction.
    \hat{k} is the unit vector in the positive z direction.
    Unit means the length of the vector is 1.

    So a point (x, y) has a position vector \vec{r} = x\hat{i} + y\hat{j}.
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    (Original post by morgan8002)
    \hat{i} is the unit vector in the positive x direction.
    \hat{j} is the unit vector in the positive y direction.
    \hat{k} is the unit vector in the positive z direction.
    Unit means the length of the vector is 1.

    So a point (x, y) has a position vector \vec{r} = x\hat{i} + y\hat{j}.
    woah buddy this is only M1
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    (Original post by Vikingninja)
    That is for a.
    well i have no idea where to start or what to do
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    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.
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    (Original post by thefatone)
    woah buddy this is only M1
    Don't worry about \hat{k} then. I don't think I've ever seen \hat{k} used in M1.
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    (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.
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    (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?
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    (Original post by morgan8002)
    \hat{i} is the unit vector in the positive x direction.
    \hat{j} is the unit vector in the positive y direction.
    \hat{k} is the unit vector in the positive z direction.
    Unit means the length of the vector is 1.

    So a point (x, y) has a position vector \vec{r} = x\hat{i} + y\hat{j}.
    Are the hats really necessary? I thought that i was already defacto the unit vector in the positive x direction, etc...
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    (Original post by thefatone)
    i got root 5 ms^-1 is that right?
    I got it as well.
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    (Original post by Zacken)
    Are the hats really necessary? I thought that i 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.
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    (Original post by Zacken)
    Are the hats really necessary? I thought that i 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.
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    (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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