(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

How much work is done by the force [tex]\vec F = (-4.0\hat\imath-6.0\hat\jmath)\;{\rm N}[/tex] on a particle that moves through displacement [tex]\Delta\vec{r}=(-3.0\hat\imath+2.0\hat\jmath)\;{\rm m}[/tex]?

2. Relevant equations

[tex]A_{x}B_{x} + A_{y}B_{y}[/tex]

3. The attempt at a solution

I decided to use the component form of the dot product method for this problem. (Or is the component form an alternative to the dot product?) Anyways, I set F as A and R as B, resulting in the following:

[tex]A_{x}B_{x} + A_{y}B_{y}[/tex]

[tex]F_{x}r_{x} + F_{y}r_{y}[/tex]

[tex]\vec F = <-4, -6>[/tex]

[tex]\vec r = <-3, 2>[/tex]

[tex]-4(-3) + (-6)(2)[/tex]

[tex]\vec C = <12,-12>[/tex]

Then I took the square root of the sum of the sqaures:

[tex]\sqrt{12^{2}+(-12)^{2}}[/tex]

[tex]\sqrt{288} \approx 17[/tex]

My answer of 17 was marked incorrect. Where did I go wrong? Any input is greatly appreciated.

I just realized that I must have made some major mistake. I just kind of "created" vector C out of nowhere. Any direction on this problem would be great.

EDIT:Nevermind, I figured out my error. Instead of creating vector C, I should have just stopped there, added 12 and -12, and got the correct answer of zero. Huzzah!

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# Homework Help: Simple Work Done by Force Problem

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