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mkwok
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Homework Statement
A force F = (5 i - 1 j) N acts on a particle that undergoes a displacement r = (2 i + j) m.
(a) Find the work done by the force on the particle. (Calculate all numerical answers to three significant figures.)
(b) What is the angle between F and r?
* the problem required us to put our answer in 4 sig figs
Homework Equations
W=F*R
cross product |F||R|cos[tex]\theta[/tex]
The Attempt at a Solution
part A,
since W=F*R, so I did: 5*2 + 1(-1) = 9.000 (4 sig figs)
Part B,
cross product |F||R|cos[tex]\theta[/tex]
|F|=[tex]\sqrt{26}[/tex]
|R| = [tex]\sqrt{3}[/tex]
9=[tex]\sqrt{26}[/tex][tex]\sqrt{3}[/tex]cos[tex]\theta[/tex]
[tex]\theta[/tex]=cos-1(9/([tex]\sqrt{26}[/tex][tex]\sqrt{3}[/tex])) = 37.87 degreesMy homework website tells me its wrong, what did I do wrong then?
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