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M1 Vectors. Stuck on past paper question watch

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    I've done from part a) to c) but I don't understand how to do d). Appreciate any help!

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    Hint: what will the i component be when P is due south? What can you say about the j component?
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    Well for it to be due south of A j should be less than -10 right? that's what I did
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    You need to say that your i components equal 0
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    (Original post by Doughnuts!!)
    You need to say that your i components equal 0
    I did, it didn't give me the right answer. Can you please be abit more specific which vectors?
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    (Original post by 5t1g)
    I did, it didn't give me the right answer. Can you please be abit more specific which vectors?
    Construct an equation with all the information you have and say that the I components equal 0. I would strongly reccomend doing it in vector notation and saying that all the I components in the equation equal 0.
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    Thanks I got the answer. But why does the i component have to equal 0 instead of the j component to be due south shouldn't it be the other way round?
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    (Original post by 5t1g)
    Thanks I got the answer. But why does the i component have to equal 0 instead of the j component to be due south shouldn't it be the other way round?
    Out of curiousity, which equation did you use? I am/was too tired to actually work out the answer to the question.

    Think about it logically; south is going downwards (the same would apply for north, which would be going upwards). Since you're only going down, you're only on the vertical plane with no horizontal components, therefore meaning that I must equal 0.

    A case where j would be 0 would be where the paricle was travelling east or east since it would only be on the horizontal plane.
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    I worked it out the time it takes to get from O (the origin) to 7i, the position vector of A. Since its speed is 2ms^2 (from part c) it takes 3.5s. so 7 + 3.5= 10.5 which is the right answer. I was working out using the wrong component before. Thanks for your help.
 
 
 
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