Anyone online?

- saifoo.khan

Anyone online?

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- schrodinger

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- saifoo.khan

Q4

##### 1 Attachment

- shadowfiend

Let me sketch out a FBD for you really quick.

- shadowfiend

Derp heh. A diagram, not a free body diagram. No forces here :p

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## More answers

- saifoo.khan

It is dealing with
v = u + at first, then s = ut + 0.5at^2

- shadowfiend

|dw:1327119231882:dw|
First move is finding when A is at its apex.

- saifoo.khan

i got 0.5 secs

- shadowfiend

You can find that by solving \(v = v_0 + at\) for t, and plugging in \(v_0 = 5\) and \(v = 0\) (since velocity is 0 at the apex), and \(-9.8ms^{-2}\) for a, since we are accelerating against gravity.

- shadowfiend

If you got 0.5s, I assume you're using \(-10ms^{-2}) as an approximate for gravity?

- saifoo.khan

Check this out..

##### 1 Attachment

- shadowfiend

I get 2.775 (= 2.8) for the s of B...

- shadowfiend

You seem to be using 7 for its velocity, it has a v_0 of 8.

- saifoo.khan

OMG! im blind.

- shadowfiend

:) It happens. The other s is right, so I'm guessing everything else will work out :)

- saifoo.khan

i get correct answer now, w.r.t marking scheme! :D
1.5N.

- shadowfiend

!! Awesome :)

- saifoo.khan

Yes!

- shadowfiend

Just watch out for those numbers :) They're sneaky little things.

- saifoo.khan

Thanks!!! ^_^

- shadowfiend

No problem!

- saifoo.khan

what about the (ii) part?

- shadowfiend

Whoops, let me have a look-see.

- mathmate

Is it part ii you want to see?

- saifoo.khan

Yes.

- shadowfiend

I'll let mathmate help heh. I got distracted trying to track down a song that's been stuck in my head all day >_<

- mathmate

I have 8t-(g/2)t^2-(5t-(g/2)t^2) = 0.9
which solves for 3t=0.9, or t=0.3 (the g... terms cancel out).
Then
height of A is 5(0.3)-(g/2)(0.3)^2 =1.0586 (using g=9.81)

- saifoo.khan

OMG! that's correct. :D

- saifoo.khan

http://www.xtremepapers.com/CIE/International%20A%20And%20AS%20Level/9709%20-%20Mathematics/9709_w02_ms_4.pdf
Page 4.

- saifoo.khan

i was confused about which one to make variable to.. hehe it was "t"/

- mathmate

Great, I guess I got too many digits, but it's easier to cut than to add! :)

- saifoo.khan

right.

- saifoo.khan

thanks!

- mathmate

Good night then... till next time!

- mathmate

You're welcome! :)

- saifoo.khan

:]

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