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Vectors in mechanics 1 watch

1. (Original post by JBKProductions)
just a question though why does it start from the x-axis and not y? i always thought you start measuring your angles from the y axis but guess i was wrong
It wouldn't really matter.

Start whereever.

Bearing of 090 would work.

Just random question, if measuring from y axis, do you go in the bearing direction (ie, to the right = positive) or go in the direction you take as positive for the x axis (ie, to the left = positive)?
2. (Original post by DaveJ)
It wouldn't really matter.

Start whereever.

Bearing of 090 would work.

Just random question, if measuring from y axis, do you go in the bearing direction (ie, to the right = positive) or go in the direction you take as positive for the x axis (ie, to the left = positive)?
Up is positive y and right is positive x, surely?
3. (Original post by ashy)
You can measure angles from wherever you like, as long as you specify what you're doing. The answer would be "0 degrees from the positive x axis" or "90 degrees from the positive y axis" etc. Both are perfectly valid, but we tend to take the normal to be +x. Still, make sure you specify it in exams.
ok so ive put 90 degrees from the positive y axis is that fine? because ive written it in pen and dont want to ruin it by crossing it out lol
4. (Original post by JBKProductions)
ok so ive put 90 degrees from the positive y axis is that fine? because ive written it in pen and dont want to ruin it by crossing it out lol
I don't see why not. You could always put in brackets afterwards that it's 0 degrees from +x if you're worried about it
5. (Original post by JBKProductions)
ok so ive put 90 degrees from the positive y axis is that fine? because ive written it in pen and dont want to ruin it by crossing it out lol
Perfect as long as you specify where the angle is being measured from.
6. (Original post by ashy)
Up is positive y and right is positive x, surely?
Hmm, I phrased my question badly.

I'm actually finding it so hard to phrase...

Hmm, if measuring angle from positive x, you move anti clockwise. But do you move clockwise if measuring from positive y, as you did in your earlier post?
7. (Original post by ashy)
I don't see why not. You could always put in brackets afterwards that it's 0 degrees from +x if you're worried about it
lol thanks
8. (Original post by DaveJ)
Hmm, I phrased my question badly.

I'm actually finding it so hard to phrase...

Hmm, if measuring angle from positive x, you move anti clockwise. But do you move clockwise if measuring from positive y, as you did in your earlier post?
Oh I see. I understand why that's hard to phrase properly! The thing is that if you have your vectors, it doesn't matter as it's obvious. If you have say 4i - 3j, then you know that the angle would be 36.9 degrees from +ve x towards -ve y.
9. (Original post by ashy)
Oh I see. I understand why that's hard to phrase properly! The thing is that if you have your vectors, it doesn't matter as it's obvious. If you have say 4i - 3j, then you know that the angle would be 36.9 degrees from +ve x towards -ve y.

Ah right, I thought you'd have had to give that as (360 - 36.9) from positive x.

Thanks.
10. (Original post by DaveJ)
Ah right, I thought you'd have had to give that as (360 - 36.9) from positive x.

Thanks.
You can if you like, just specify that that's what you're doing
11. (Original post by ashy)
Oh I see. I understand why that's hard to phrase properly! The thing is that if you have your vectors, it doesn't matter as it's obvious. If you have say 4i - 3j, then you know that the angle would be 36.9 degrees from +ve x towards -ve y.
sorry for butting in the convo but couldnt i write the bearing as 126.9 degrees?
12. (Original post by JBKProductions)
sorry for butting in the convo but couldnt i write the bearing as 126.9 degrees?
Yes.
13. (Original post by DaveJ)
Yes.
ok thanks

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