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m1 urgent doubt :/

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sweetest angel:
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 :)

halosh92:

--- 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 :)

--- End quote ---

how did u do part a?

sweetest angel:
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 :)

Phosu:
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

halosh92:

--- 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 :)

--- End quote ---

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

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