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# Really struggling with M1 watch

1. (Original post by samb1234)
OK before I give you the full solution I'll try and lead you through it as it will be more useful than me just telling you how to do it. What have you done on the last question so far?

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So I said let the position vector of the Lighthouse be (xi + yj)
then I plugged in 1 in the equation in the previous part and made it equal to x

then I plugged in 1.5 to the equation in the previous part and made the i vector equal to -1 and the j vector equal to 1.?
2. (Original post by frozo123)
So I said let the position vector of the Lighthouse be (xi + yj)
then I plugged in 1 in the equation in the previous part and made it equal to x

then I plugged in 1.5 to the equation in the previous part and made the i vector equal to -1 and the j vector equal to 1.?
Try doing this. Firstly work out the position vector of the boat at both t =1 and t =1.5. As the lighthouse is directly west at 10 am, what can you deduce about the J component of the lighthouses position vector?

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3. (Original post by samb1234)
Try doing this. Firstly work out the position vector of the boat at both t =1 and t =1.5. As the lighthouse is directly west at 10 am, what can you deduce about the J component of the lighthouses position vector?

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the J component of the lighthouse is 0?
4. (Original post by frozo123)
the J component of the lighthouse is 0?
Correct. Now if I move south west, the distance I move down is the distance I move west. Can you work it out from there?

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5. (Original post by samb1234)
Correct. Now if I move south west, the distance I move down is the distance I move west. Can you work it out from there?

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yes but if you gave me another question and it wasn't the same format I wouldn't be able to do it
6. (Original post by frozo123)
yes but if you gave me another question and it wasn't the same format I wouldn't be able to do it
Its exactly the same principle every time

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7. (Original post by samb1234)
Its exactly the same principle every time

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the questions are always different, for example when Ship A is moving (2i-3j) of Ship B? you wouldn't use that method would you?
8. (Original post by frozo123)
the questions are always different, for example when Ship A is moving (2i-3j) of Ship B? you wouldn't use that method would you?
There is some variation but they are all essentially using the same prinicples

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9. (Original post by samb1234)
There is some variation but they are all essentially using the same prinicples

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may you give me some instructions on what to learn please?
10. (Original post by frozo123)
may you give me some instructions on what to learn please?
I mean in maths you can't really 'revise' as such. I would recommend that you look back at the vectors chapter in the textbook and between that and past papers just do as many questions as you can. The more you practice, the easier questions will get

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