Hey please help me guys...

- rvc

Hey please help me guys...

- Stacey Warren - Expert brainly.com

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- katieb

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- rvc

im solving old university question papers..
for the verification of answers n doubts i require your help ....

- rvc

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- IrishBoy123

gotcha
which one you doing, all of them?

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## More answers

- rvc

yep all
this is just question 1
thank you so much sir :)
this help of yours will surely bring a lot of difference in my understanding of mechanics in particular since im not so good at it. :)

- IrishBoy123

|dw:1447165187900:dw|
assuming frictionless wall

- rvc

i got T as 11.547N

- IrishBoy123

yeah
ihttp://www.wolframalpha.com/input/?i=10%2F+sin%2860%29
soz, i haven't got a proper calculator

- rvc

i applied lami's theorem here |dw:1447165361043:dw|

- IrishBoy123

i don't know what lami is, would need to look it up....
|dw:1447165525622:dw|
i would just resolve in x direction: \(R - T \cos (60) = 0\)

- IrishBoy123

ah, Lami:
\[\frac{A}{\sin \alpha}=\frac{B}{\sin \beta}=\frac{C}{\sin \gamma}\]
could do that i suppose....

- rvc

yep
what did you get the answer as?

- IrishBoy123

http://www.wolframalpha.com/input/?i=+cos%2860%29+*+10%2F+sin%2860%29

- IrishBoy123

\( 10 / \sqrt{3} \)

- rvc

hmmm its different

- rvc

how did u get cos?

- IrishBoy123

|dw:1447165867289:dw|
\(R - T \cos (60) = 0\)
\(\implies R = \dfrac{W}{\sin (60)} . \cos (60) \)

- rvc

|dw:1447166144735:dw|

- rvc

hmm
|dw:1447166267615:dw|

- IrishBoy123

http://www.wolframalpha.com/input/?i=10*sin%28150%29+%2F+sin%28120%29

- IrishBoy123

same answer
ie \[\dfrac{T}{\sin (90)} = \dfrac{R}{\sin (150)} = \dfrac{10}{\sin (120)}\]

- rvc

150?

- IrishBoy123

|dw:1447166630689:dw|

- rvc

oh okay
got it
ty
1 d)
n 1 e)

- IrishBoy123

1 d)
|dw:1447166827568:dw|

- IrishBoy123

that's (i) & (ii)

- rvc

yep

- IrishBoy123

|dw:1447166911099:dw|

- IrishBoy123

in terms of the words, well i hate wordy questions, especially when a drawing is an awful lot more powerful....

- rvc

yep i understand :)
yes this answer was correct of mine however i m struggling with the next one

- IrishBoy123

e?

- IrishBoy123

this is a v-t graph. the area under the graph gives the displacement, in this case the distance travelled by the plane. so you can add them up to help create the s-t graph
|dw:1447167306987:dw|

- mathmate

ok, are we still on the centroid problem?

- rvc

yep

- mathmate

I'll give a simple example of compound areas, ok?

- rvc

yep
with the rotating stuff

- mathmate

I'll start with something really simple, and then we'll work on the rotation.
The idea of finding centroid of multiple areas is relatively simple.
You would take moments about the x-axis of each area, add them up, and divide by the total area.
In math terms, it would be
\(\Large xbar = \frac{\sum (Ax)}{\sum(A)}\)

- mathmate

* about y-axis
Does that look familiar to you?

- rvc

yep
similarly we have for y co-ordinate of centroid

- mathmate

Exactly!
Would you like to work on this one?
|dw:1447214876953:dw|

- mathmate

|dw:1447214987394:dw|

- rvc

sure :)

- mathmate

Go ahead, I'll watch.

- rvc

bigger rectangle : A =8 x=2 y = 1
smaller rect : A =4 x= 1 y = 3
summation Ax= 20 , Ay= 20
X = 6.667, Y =5
X,Y(6.667,5) units
well since the units are not mentioned i did not consider any units

- mathmate

Excellent, so we'll now tackle the other one.
I'll redraw the figure.

- mathmate

|dw:1447215425315:dw|

- mathmate

so far so good?
can you now calculate theta and phi (we need only the sum).

- mathmate

|dw:1447215537063:dw|

- rvc

theta = 36.8698
phi =5?

- rvc

sorry

- rvc

one sec pls

- mathmate

|dw:1447215594219:dw|

- rvc

phi is 2.7158?

- mathmate

I have theta=36.86990
phi=59.86691
Do you agree?

- rvc

i agree with theta
but not with phi :(

- mathmate

Sorry, that would be the sum, phi=22.99701

- rvc

nope 2.715?

- mathmate

phi is atan(1.06103/2.5), do you agree?

- rvc

yesss

- rvc

well i gt 2.715

- mathmate

You forgot the parenthesis for atan! lol

- rvc

ohh i gt u
sorry i thought u r considering lenght
lol

- rvc

22.9963?

- mathmate

ok, length is 2.71584, yes.

- mathmate

We need the length and (phi+theta) in order to calculate x' and y'.

- mathmate

Actually I should rename them x2, y2.
And the one for the triangle x1,y1.

- mathmate

still there?

- rvc

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