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Author Topic: phys doubt  (Read 5858 times)

Offline Phosu

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Re: phys doubt
« Reply #45 on: March 28, 2010, 04:04:01 pm »
A particle is acted upon by two forces F1 and F2 , given by
F1 = (i – 3j) N,
F2 = ( pi + 2pj) N, where p is a positive constant.
(a) Find the angle between F2 and j

how do we find the angle?
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Offline astarmathsandphysics

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Re: phys doubt
« Reply #46 on: March 28, 2010, 04:08:25 pm »
Cos x =u.v/|u||v|
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Offline halosh92

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Re: phys doubt
« Reply #47 on: March 28, 2010, 04:56:54 pm »
Quote from: astarmathsandphysics on March 28, 2010, 04:08:25 pm
Cos x =u.v/|u||v|

could you expalin in  details plz?
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everyday we wake up is a miracle, then how do we say miracles dont happen?????

Offline astarmathsandphysics

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Re: phys doubt
« Reply #48 on: March 28, 2010, 05:19:21 pm »
F1 = (i – 3j) N,
F2 = ( pi + 2pj) N, where p is a positive constant.
F1.F2=1*p+-3*2p=-5p
|F1|=sqrt(1^2+(-3)^2)=sqrt(10)
|F2|=sqrt(p^2+(2p)^2)=sqrt(5p^2)
cos theta=-5p/sqrt(10)sqrt(5p^2)=5over sqrt(50)=1/sqrt(2)
theta=cos^-1 1/sqrt()=45
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