more ops

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Gasket18
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Posts: 70
Joined: Aug 2019

more ops

Postby Gasket18 » Sat Jul 3 2021, 02:00

Ok all thanks for the answers so far. I'm still plugging away have another 4 weeks until I'm allowed to drive again so hopefully it'll all sink into my head by then. Doing some more c of g movement questions at the moment. And wondering if there is a simpler way to these calcs than the way I've worked out. I've attached a screenshot of the type of questions. ok edited post as pic wouldnt attach for some reason. I'll explain my thinking of q1

Given details are: weight 1578.4 kg moment 50303.608 and arm 3187 if you move 1 rear pax 65kg and place in front row what will this effect have on the cg? and will cg be within limits?

I took the 65kg pax from row 3 and resultant moment 65 x 3276.7 = 2129.855
giving me a new moment of 48173.753
then calculated the 65kg in row 1 65 x 1651 = 1073.15
which gives new moment of 49246.903 x 100 / by weight 1578.4
gives new arm of 3120.1 which was correct answer yay
just wondering if there is a more efficient way of doing it, or the way I have figured is what it is.
Thanks
Chopper Guy
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Joined: Oct 2011

Re: more ops

Postby Chopper Guy » Sat Jul 3 2021, 03:09

Hey Mate

The method you've used is perfectly acceptable and will get you through the exam.

CG
DADFA
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Posts: 28
Joined: Mar 2013

Re: more ops

Postby DADFA » Sat Jul 3 2021, 13:01

The formula
Wt to shift=(GW x C of G shift distance) divided by Net arm between stations (net arm is the difference between the arms of the station you are shifting from and the one you are shifting to.)

gives C of G Shift distance = (Wt to shift x Net arm) divided by GW

so 65 x 1625.7 / 1578.4 =66.94 or 67.00 rounded.
subtract this from 3187, the original arm, gives 3120 your new arm.

Use it or not your way is just as valid.
Gasket18
Silver Wings
Silver Wings
Posts: 70
Joined: Aug 2019

Re: more ops

Postby Gasket18 » Sun Jul 4 2021, 12:11

Thanks Dadfa and chopper guy. Thanks for showing that working. Sometimes I can't see how formula works. So kind of go off on my own and figure something out. I'll play with this one for a while and see if it's quicker. Yeah mine worked chopper I was just seeing if there was a faster way, as the performance exam is very time critical. I had one attempt before I was ready and couldn't believe how much time was chewed up just trying to do my formulas. All my other exams finding an answer took nowhere near as long. Hopefully this will all get quicker.

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