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Old Jul 13th 2018, 08:33 AM   #1
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Lightbulb The angle between P and Q?

The resultant R of vectors P and Q is perpendicular to P and R=P both, then the angle between P and Q is what?
Now, what is the concept behind it? Could you provide me with an image of the resultant perpendicular to two vectors so that I can understand the concept and start solving the problem?
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Old Jul 13th 2018, 09:29 AM   #2
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Please clarify what you mean by the phrase "R=P both" - are you trying to say that the magnitude of vector R = the magnitude of vector P?

Keep in mind that for vector R (which is the sum of vectors P and Q) to be perpendicular to P, the vector Q must have a component in the negative P direction that is equal in magnitude to the magnitude of P, and Q must also have a component that is perpendicular to P.
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Old Jul 13th 2018, 09:56 AM   #3
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Lightbulb

Originally Posted by ChipB View Post
Please clarify what you mean by the phrase "R=P both" - are you trying to say that the magnitude of vector R = the magnitude of vector P?

Keep in mind that for vector R (which is the sum of vectors P and Q) to be perpendicular to P, the vector Q must have a component in the negative P direction that is equal in magnitude to the magnitude of P, and Q must also have a component that is perpendicular to P.
Could you please get your points a little bit easier with a diagram so that I can understand the concept well?
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Old Jul 13th 2018, 10:36 AM   #4
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Go back to you original definition of vector addition by the parallelogram law.

Start by drawing vector P.

From the same origin O, draw vector R the same length and at right angles to P.
This will be the diagonal resultant of your parallelogram.

Join the ends of the vectors R and P, noting the angle alpha as shown.

Complete the parallelogram by drawing the vector OQ parallel to RP.

Thus you can find the angle required by simple geometry.

I will leave it to ChipB use these diagrams to explain what he means by components if he wants.
Attached Thumbnails
The angle between P and Q?-vectorpllm1.jpg  
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Last edited by studiot; Jul 13th 2018 at 03:18 PM. Reason: spelling
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Old Jul 13th 2018, 09:40 PM   #5
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Originally Posted by studiot View Post
Go back to you original definition of vector addition by the parallelogram law.

Start by drawing vector P.

From the same origin O, draw vector R the same length and at right angles to P.
This will be the diagonal resultant of your parallelogram.

Join the ends of the vectors R and P, noting the angle alpha as shown.

Complete the parallelogram by drawing the vector OQ parallel to RP.

Thus you can find the angle required by simple geometry.

I will leave it to ChipB use these diagrams to explain what he means by components if he wants.
Thanks a lot. So kind of you.
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