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	<title>ETF2L &#8211; Latest activity in &#8220;fucking suvat&#8221;</title>
	<link>https://staging.etf2l.org/forum/off-topic/topic-13342/</link>
	<description><![CDATA[The latest posts to this topic.]]></description>
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    	    <title>Reply by vlad_drac</title>
    	    <link>https://staging.etf2l.org/forum/off-topic/topic-13342/page-2/?recent=231153#post=231153</link>
    	    <description><![CDATA[Oh, btw.. i think you were right eehee, i found it too hard to follow and instead i just plugged away for a bunch of hours getting my head around it, got the right answer eventually too.

Better that i did really, because now i understand it really really well :P]]></description>
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    	    <pubDate>Tue, 12 Oct 2010 16:16:46 +0200</pubDate>
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    	    <title>Reply by Rochester</title>
    	    <link>https://staging.etf2l.org/forum/off-topic/topic-13342/page-2/?recent=231153#post=227151</link>
    	    <description><![CDATA[I didn't go out through all the replies, but since this doesn't end with a post of OP being the epitome of thankfulness, I supose there isn't a solution yet?

We have: y(t0)=0, x(t0)=0, y(te)=-30, x(te)=30 (this only matters because of signs)

Denote the initial velocity as v0. That's what we are looking for. It has an x- and an y-component, for which we derive the motion equations. Since there is no friction we obtain:

dotx(t)=cos(34°)*v0 (constant)
doty(t)=sin(34°)*v0-g*t (g*t is negative because the ball is initially thrown upward)

We integrate this, thus obtaining position equations &#38; fill in the initial and final condition (note that we have chosen x0=y0=0):

30=v0*te*cos(34°)
-30=v0*te*sin(34°)-0.5*g*te^2

Two equations, two unknowns :)]]></description>
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    	    <pubDate>Sun, 03 Oct 2010 20:20:49 +0200</pubDate>
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    	    <title>Reply by Davib</title>
    	    <link>https://staging.etf2l.org/forum/off-topic/topic-13342/page-2/?recent=231153#post=227127</link>
    	    <description><![CDATA[disregard what I wrote, the guy below me has it. I was overcomplicating it.]]></description>
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    	    <pubDate>Sun, 03 Oct 2010 19:34:43 +0200</pubDate>
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    	    <title>Reply by vlad_drac</title>
    	    <link>https://staging.etf2l.org/forum/off-topic/topic-13342/page-2/?recent=231153#post=227119</link>
    	    <description><![CDATA[Given myself a migraine by stupidly spending 7 hours on and off staring at this trying to work it out.  Taking a break from it today.  Not saying anyone's right or wrong, but so far i've either not been able to follow what people were saying (either cos they're not showing their working or because it's just hard via an internet forum) or they've got a different answer than the stated one.]]></description>
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    	    <pubDate>Sun, 03 Oct 2010 19:26:20 +0200</pubDate>
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    	    <title>Reply by ilike2spin</title>
    	    <link>https://staging.etf2l.org/forum/off-topic/topic-13342/page-2/?recent=231153#post=227089</link>
    	    <description><![CDATA[ahha! that's what suvat means, I've never heard it being referred to as that before.]]></description>
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    	    <pubDate>Sun, 03 Oct 2010 19:03:47 +0200</pubDate>
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    	    <title>Reply by Dr. Chris</title>
    	    <link>https://staging.etf2l.org/forum/off-topic/topic-13342/page-2/?recent=231153#post=227087</link>
    	    <description><![CDATA[<i>Quoted from Chaplain</i>
		<blockquote>[...]

lolthx Chris. I've written the Horizontal Accel as 0, not as 1, so i'll re do it from there

now we use S=ut+1/2at^2 again

S=xt+1/2t^2 (as a=1)

30=2.47x + 1/2*2.47^2

x=10.91m/s

x(Initial Speed) to 2sf=11m/s

Lol thanks Chris, epic fail on my part there</blockquote>

did i just get trolled? :(]]></description>
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    	    <pubDate>Sun, 03 Oct 2010 19:01:23 +0200</pubDate>
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    	    <title>Reply by Davib</title>
    	    <link>https://staging.etf2l.org/forum/off-topic/topic-13342/page-2/?recent=231153#post=227079</link>
    	    <description><![CDATA[edit: ignore what I wrote here, IM A MORON]]></description>
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    	    <pubDate>Sun, 03 Oct 2010 18:50:34 +0200</pubDate>
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    	    <title>Reply by ErrorOperator</title>
    	    <link>https://staging.etf2l.org/forum/off-topic/topic-13342/page-2/?recent=231153#post=227077</link>
    	    <description><![CDATA[Hey guys this thread at the moment is too clever for www.etf2l.org to handle. So I will just leave this post here.]]></description>
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    	    <pubDate>Sun, 03 Oct 2010 18:48:44 +0200</pubDate>
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    	    <title>Reply by adam-skyride</title>
    	    <link>https://staging.etf2l.org/forum/off-topic/topic-13342/page-2/?recent=231153#post=227075</link>
    	    <description><![CDATA[nvm, fail]]></description>
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    	    <pubDate>Sun, 03 Oct 2010 18:46:56 +0200</pubDate>
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    	    <title>Reply by weaselo</title>
    	    <link>https://staging.etf2l.org/forum/off-topic/topic-13342/page-2/?recent=231153#post=227070</link>
    	    <description><![CDATA[<i>Quoted from vlad_drac</i>
		<blockquote>I know what you mean, yeah.  But do you know what i mean? :/

If he's throwing it at an angle upwards, we don't know the initial horizontal or vertical speed.  We don't know the time, we only know the horizontal distance (for uneven ground) and the vertical acceleration.

If you do a quick diagram yourself, i think you might see what i mean.  Whether it's vcos34 or vsign34, it's still a proportion of a variable that we don't know.


So basically, we know we know horizontal accel is 0, horizontal displacement is 30.</blockquote>

But if we know what vcos34= and what vsin34= by splitting the parabolic motion and calculating horizontal and vertical, then we can work out v by using simultaneous equations, showing us the unknown proportion. Now i really need to sleep, If I get time when i wake up, ill grab some paper, as i have a notion that I'm not really coming across with what i actually mean :P

I imagine i'll remember how to do it soon enough, as it looks very similar to the kind of thing I would have tackled a few years ago in Further mechanics (if its solveable ofc)]]></description>
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    	    <pubDate>Sun, 03 Oct 2010 18:33:12 +0200</pubDate>
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    	    <title>Reply by vlad_drac</title>
    	    <link>https://staging.etf2l.org/forum/off-topic/topic-13342/page-1/?recent=231153#post=227066</link>
    	    <description><![CDATA[<i>Quoted from Zeks</i>
		<blockquote>horizontally:
30 = utcos(34)

vertically:

v = usin(34) + gt
Using the equation derived from the horizontal motion we see:
v = usin(34) + 30g/(ucos(34))
(v^2 = (usin34)^2 + 900g^2/(ucos34)^2 + 60gtan34)
using v^2 = u^2 + 2as we see:
v^2 = (usin34)^2 + 60g)

hence 
60g = 60gtan(34) + 900g^2/(ucos34)^2
1-tan34 = 15g/(ucos34)^2
u=25.6ms^-1

this might be wrong i cba to check</blockquote>

You lost me a few steps along there, and the answer's wrong too :(]]></description>
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    	    <pubDate>Sun, 03 Oct 2010 18:29:44 +0200</pubDate>
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    	    <title>Reply by Zeks</title>
    	    <link>https://staging.etf2l.org/forum/off-topic/topic-13342/page-1/?recent=231153#post=227062</link>
    	    <description><![CDATA[horizontally:
30 = utcos(34)

vertically:

v = usin(34) + gt
Using the equation derived from the horizontal motion we see:
v = usin(34) + 30g/(ucos(34))
(v^2 = (usin34)^2 + 900g^2/(ucos34)^2 + 60gtan34)
using v^2 = u^2 + 2as we see:
v^2 = (usin34)^2 + 60g)

hence 
60g = 60gtan(34) + 900g^2/(ucos34)^2
1-tan34 = 15g/(ucos34)^2
u=25.6ms^-1

this might be wrong i cba to check]]></description>
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    	    <pubDate>Sun, 03 Oct 2010 18:19:16 +0200</pubDate>
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    	    <title>Reply by vlad_drac</title>
    	    <link>https://staging.etf2l.org/forum/off-topic/topic-13342/page-1/?recent=231153#post=227061</link>
    	    <description><![CDATA[I know what you mean, yeah.  But do you know what i mean? :/

If he's throwing it at an angle upwards, we don't know the initial horizontal or vertical speed.  We don't know the time, we only know the horizontal distance (for uneven ground) and the vertical acceleration.

If you do a quick diagram yourself, i think you might see what i mean.  Whether it's vcos34 or vsign34, it's still a proportion of a variable that we don't know.

So basically, we know we know horizontal accel is 0, horizontal displacement is 30.]]></description>
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    	    <pubDate>Sun, 03 Oct 2010 18:18:31 +0200</pubDate>
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    	    <title>Reply by weaselo</title>
    	    <link>https://staging.etf2l.org/forum/off-topic/topic-13342/page-1/?recent=231153#post=227054</link>
    	    <description><![CDATA[<i>Quoted from vlad_drac</i>
		<blockquote>Hard via text, i know, but:

- Lets work out the vertical, so we know the time it takes to hit the ground
- S-30m
- U-0
- V-?
- A-9.8
- T-?

Why have you started with initial vertical velocity as 0?  The basketball starts with speed s at 53 degrees above the horizontal, so the initial vertical velocity is s * sin 53, and we don't know what s is.

Also in your edit, why is a=1?  horizontal acceleration is 0, vertical acceleration is 9.18

---

Also, i'm gonna go back on myself on that one, i think the horizontal range in this case means when it hits the floor at the bottom of the cliff.  There is a formula for uneven ground but you're not gonna like it:

http://en.wikipedia.org/wiki/Range_of_a_projectile#Uneven_Ground

Believe me, sticking values into that gives you something like 3.5 million on one side of the equation, and v^4, v^2 and v on the other side.</blockquote>

I originally had a=0, but I changed it due to Chris putting 0==1 or whatever, but I probably shouldn't have. If you put the a=0, then the final answer is 12 m/s. The method is still correct, so just do it any way you like. i can't be arsed to change the a back to the way it was in the first place.

I didnt actually read that he threw it at an angle, which was silly of me. You should draw a diagram to equalise it into Horizontal and Vertical speeds/forces and take it from there, continuing with the parabolic method I've done above (with a=0). If he threw it at a purely horizontally, then my method would be correct, so just equalise the forces with the xcos() method. I'm gonna go sleep, if you still havent got it later, then ill show you what i mean]]></description>
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    	    <pubDate>Sun, 03 Oct 2010 17:56:42 +0200</pubDate>
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    	    <title>Reply by vlad_drac</title>
    	    <link>https://staging.etf2l.org/forum/off-topic/topic-13342/page-1/?recent=231153#post=227051</link>
    	    <description><![CDATA[Hard via text, i know, but:

- Lets work out the vertical, so we know the time it takes to hit the ground
- S-30m
- U-0
- V-?
- A-9.8
- T-?

Why have you started with initial vertical velocity as 0?  The basketball starts with speed s at 53 degrees above the horizontal, so the initial vertical velocity is s * sin 53, and we don't know what s is.  If you take it from the top of its parabola, vertical speed is 0, but then we don't know the height anymore.

Also in your edit, why is a=1?  horizontal acceleration is 0, vertical acceleration is 9.18.  So actually 1/2 at^2 would cancel out to 0.

---

Also, i'm gonna go back on myself on that one, i think the horizontal range in this case means when it hits the floor at the bottom of the cliff.  There is a formula for uneven ground but you're not gonna like it:

http://en.wikipedia.org/wiki/Range_of_a_projectile#Uneven_Ground

Believe me, sticking values into that gives you something like 3.5 million on one side of the equation, and v^4, v^2 and v on the other side.]]></description>
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    	    <pubDate>Sun, 03 Oct 2010 17:44:23 +0200</pubDate>
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