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Author Topic: m1 urgent doubt :/  (Read 1585 times)

Offline sweetest angel

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m1 urgent doubt :/
« on: March 28, 2010, 04:54:04 pm »
Two forces, (4i – 5j) N and (pi + qj) N, act on a particle P of mass m kg. The resultant
of the two forces is R. Given that R acts in a direction which is parallel to the
vector (i – 2j),
(a) find the angle between R and the vector j,

(b) show that 2p + q + 3 = 0.

Given also that q = 1 and that P moves with an acceleration of magnitude 8?5 m s–2,
(c) find the value of m.

i need someone to xplain part b asap...Thanks :)
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Offline halosh92

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Re: m1 urgent doubt :/
« Reply #1 on: March 28, 2010, 05:01:02 pm »
Quote from: sweetest angel on March 28, 2010, 04:54:04 pm
Two forces, (4i – 5j) N and (pi + qj) N, act on a particle P of mass m kg. The resultant
of the two forces is R. Given that R acts in a direction which is parallel to the
vector (i – 2j),
(a) find the angle between R and the vector j,

(b) show that 2p + q + 3 = 0.

Given also that q = 1 and that P moves with an acceleration of magnitude 8?5 m s–2,
(c) find the value of m.

i need someone to xplain part b asap...Thanks :)

how did u do part a?
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Offline sweetest angel

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Re: m1 urgent doubt :/
« Reply #2 on: March 28, 2010, 05:16:32 pm »
tan? = 2/1

?? = 63.4
angle is 90+63.4=153.4

its because it is parallel to (i-2j) so they'l have the same angel

bdw its 2laa2 ya halla :)
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"Dont fear the creation, but fear the creator who has created the creation you fear"
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Offline Phosu

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Re: m1 urgent doubt :/
« Reply #3 on: March 28, 2010, 05:26:43 pm »
b part, add the 2 vector forces to give the resultant force

the resultant force vector is parallel to the (i-2j) vector, hence gradient will be same
formula is i1/i2 = j1/j2

Ri /i = Rj /-2

4+p/1= q-5/-2

cross multiply to get
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Offline halosh92

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Re: m1 urgent doubt :/
« Reply #4 on: March 28, 2010, 05:37:47 pm »
Quote from: sweetest angel on March 28, 2010, 05:16:32 pm
tan? = 2/1

?? = 63.4
angle is 90+63.4=153.4

its because it is parallel to (i-2j) so they'l have the same angel

bdw its 2laa2 ya halla :)

hahhaah mana 3arfa ya otah ;)
thx..am failing mechanics tomorrow -.-"
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Offline sweetest angel

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Re: m1 urgent doubt :/
« Reply #5 on: March 28, 2010, 05:44:31 pm »
Quote from: Phosu on March 28, 2010, 05:26:43 pm
b part, add the 2 vector forces to give the resultant force

the resultant force vector is parallel to the (i-2j) vector, hence gradient will be same
formula is i1/i2 = j1/j2

Ri /i = Rj /-2

4+p/1= q-5/-2

cross multiply to get

no i didnt get it :/...why did u divide them by the vector that they are parallel to?

lol haloosh evryone is sayin dat :P
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"Dont fear the creation, but fear the creator who has created the creation you fear"
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Offline halosh92

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Re: m1 urgent doubt :/
« Reply #6 on: March 28, 2010, 06:21:03 pm »
Quote from: sweetest angel on March 28, 2010, 05:44:31 pm
no i didnt get it :/...why did u divide them by the vector that they are parallel to?

lol haloosh evryone is sayin dat :P

i didnt get it either poshuuuuuuuuuuuuuu expalin
or someone god dammit
where did u get this question from alooa???
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Amr Fouad

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Re: m1 urgent doubt :/
« Reply #7 on: March 28, 2010, 06:36:36 pm »
2 MINUTES..
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Offline Phosu

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Re: m1 urgent doubt :/
« Reply #8 on: March 28, 2010, 06:38:36 pm »
it says the R is parallel to (i-2j)
that means gradients will be equal.

how do we get the gradient from a coordinate
y/x right?

so whats the gradient for R vector

q-5/4+p

now m for (i-2j)  note:- i is also equal to 1i which is 1
so the gradient for this will be, -2/1

equate the gradients
q-5/4+p = -2/1

so you get, q-5= -2(4+p)

yay i feel so smart! :D
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Amr Fouad

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Re: m1 urgent doubt :/
« Reply #9 on: March 28, 2010, 07:07:14 pm »
Her You Go..

Hope that helps..

  :D
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Offline halosh92

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Re: m1 urgent doubt :/
« Reply #10 on: March 28, 2010, 09:20:33 pm »
thxxx alooot ;D ;D ;D
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everyday we wake up is a miracle, then how do we say miracles dont happen?????

Amr Fouad

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Re: m1 urgent doubt :/
« Reply #11 on: March 28, 2010, 09:22:58 pm »
any time ;)
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