Physics Help Forum Forces in vectors Calculation

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 Dec 8th 2018, 02:10 PM #1 Junior Member   Join Date: Dec 2018 Posts: 3 Forces in vectors Calculation Hi please refer to the image for the question. Attached Thumbnails
Dec 10th 2018, 06:23 AM   #2
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 Originally Posted by KyleFresh Hi please refer to the image for the question.
So... what do you think?

Do you know what the difference is between $\displaystyle v$, $\displaystyle v_x$ and $\displaystyle v_y$?

Dec 11th 2018, 12:54 PM   #3
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 Originally Posted by benit13 So... what do you think? Do you know what the difference is between $\displaystyle v$, $\displaystyle v_x$ and $\displaystyle v_y$?
I got Fnetx= vcosθ - cv^2cosθ

Dec 12th 2018, 02:00 AM   #4
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 Originally Posted by KyleFresh I got Fnetx= vcosθ - cv^2cosθ
Okay... but do you know what the difference is between $\displaystyle v$, $\displaystyle v_x$ and $\displaystyle v_y$? It's important because once you know that, you'll find the question a lot easier.

Last edited by benit13; Dec 12th 2018 at 05:46 AM.

 Dec 12th 2018, 02:53 AM #5 Senior Member     Join Date: Jun 2016 Location: England Posts: 786 There is a standard maths technique for separating a vector into separate components, acting in different directions. (2 components for a 2D vector, 3 for a 3D vector, etc.) By convention these components are at 90 degrees with respect to each other. (It is possible to define and use components that are not at 90 degrees, but that is another story). There are standard mathematical rules for what happens to each component of a vector when a mathematical operation is applied to the main vector. If you are familiar with those rules, then the answer is obvious. If you are not familiar with those rules, seek additional guidance from your tutor. The whole point of your tutor giving you these questions is to identify any holes in your understanding, and if they are a good tutor they will then try to fix those holes. topsquark and benit13 like this. __________________ ~\o/~
 Dec 13th 2018, 08:32 PM #6 Junior Member   Join Date: Dec 2018 Posts: 3 I don't have tutor. I'm a University student who can't afford a tutor.
 Dec 14th 2018, 06:33 AM #7 Forum Admin     Join Date: Apr 2008 Location: On the dance floor, baby! Posts: 2,554 The writers of the problem are trying to mess with you a bit. The answer is B). The x-component of the force is $\displaystyle F~cos( \theta )$, so the x component of the force in this case is $\displaystyle -c v^2 ~ cos( \theta )$. The trick is that we can break this down into $\displaystyle -c v^2~cos( \theta ) = -c v \cdot v~cos( \theta ) = -c v \cdot v_x$ Frankly I think this is a lousy problem for this level. It's more a test of your Algebra than your Physics knowledge, and the negative sign is somewhat arbitrary. -Dan __________________ Do not meddle in the affairs of dragons for you are crunchy and taste good with ketchup. See the forum rules here.
Dec 16th 2018, 12:51 PM   #8
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 Originally Posted by KyleFresh I don't have tutor. I'm a University student who can't afford a tutor.
I can tutor you for free if you'd like. I did a lot of tutoring in college and have spent years in forums helping people. What I won't do is simply give answers or help when you haven't shown your attempt.

Sound good?

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