tilting and slipping friction forces help Watch

ddsizebra
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Please someone help me? I keep getting close to the right answer but not quite.Name:  New Doc 2019-04-18 11.53.58_1(2)-compressed.jpg.jpeg
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Size:  77.5 KBName:  New Doc 2019-04-18 11.53.58_2(2)-compressed.jpg.jpeg
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N.B. I messed up on second half so I cut it out from my workings.
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mqb2766
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What answer were you given?

Edit - the 2nd line of your horizontal force looks a bit dodgy. Im presuming Fs = Fx, but even so, it looks like there is a sign wrong, as Pcos must be equal to the sum of the other two forces which hinder motion?
(Original post by ddsizebra)
Please someone help me? I keep getting close to the right answer but not quite.Name:  New Doc 2019-04-18 11.53.58_1(2)-compressed.jpg.jpeg
Views: 9
Size:  77.5 KBName:  New Doc 2019-04-18 11.53.58_2(2)-compressed.jpg.jpeg
Views: 9
Size:  105.4 KB
N.B. I messed up on second half so I cut it out from my workings.
Last edited by mqb2766; 1 month ago
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ddsizebra
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sorry, already solved it! I forget the split N into horizontal and vertical components... 😪
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ddsizebra
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Name:  New Doc 2019-04-18 13.30.36_1-compressed.jpg.jpeg
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Size:  81.5 KB another issue, I cannot do C. Basically I replaced 9.81 earth's gravity with 1.6 moon's gravity and converted the 400N back into kg and then multiplied by moon's gravity.
But my answer is wrong for some reason
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mqb2766
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So what did you get for c)?
They've done 21.6*9.8/1.6 to get 132.5kg.
The thing is, gravity (moon or earth) is a linear multiplier on both sides of the equation as its balance of forces, and all forces depend on gravity. Why isn't the mass the same? Its as though they've assumed the 400N for the packing case is constant, but it depends on gravity?
(Original post by ddsizebra)
Name:  New Doc 2019-04-18 13.30.36_1-compressed.jpg.jpeg
Views: 9
Size:  81.5 KB another issue, I cannot do C. Basically I replaced 9.81 earth's gravity with 1.6 moon's gravity and converted the 400N back into kg and then multiplied by moon's gravity.
But my answer is wrong for some reason
Last edited by mqb2766; 1 month ago
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ddsizebra
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(Original post by mqb2766)
So what did you get for c)?
They've done 21.6*9.8/1.6 to get 132.5kg.
The thing is, gravity (moon or earth) is a linear multiplier on both sides of the equation as its forces, and both forces depend on gravity. Why isn't it the mass the same? Its as though they've assumed the 400N for the packing case is constant, but it depends on gravity?
But I thought we had to take the earth's gravity to get the box actual weight then multiply that by the moon's gravity
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mqb2766
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You have weights on both sides. Convert them both to masses (divide by earth gravity) and then multiply them both by moon gravity. The balance equation still holds?
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ddsizebra
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(Original post by mqb2766)
You have weights on both sides. Convert them both to masses (divide by earth gravity) and then multiply them both by moon gravity. The balance equation still holds?
I think I get it. Thanx!
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mqb2766
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I wish your book did :-( ...
(Original post by ddsizebra)
I think I get it. Thanx!
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ddsizebra
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one more (hopefully). How do you question C? I'm assuming it means where I drew the question mark... Name:  New Doc 2019-04-18 14.16.38-compressed.jpg.jpeg
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Name:  New Doc 2019-04-18 14.18.46-compressed.jpg.jpeg
Views: 10
Size:  67.6 KB

n.b. what do you mean by book?
p.s. I've has less than 4 hours sleep last night as I work full time - which is why I'm asking dumb ass question...so appologies if this make me look stupid.
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mqb2766
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I meant the model solutions which are given for the questions, no offence was meant to you. We all make mistakes, its how you learn.
(Original post by ddsizebra)
one more (hopefully). How do you question C? I'm assuming it means where I drew the question mark... Name:  New Doc 2019-04-18 14.16.38-compressed.jpg.jpeg
Views: 10
Size:  71.9 KB
Name:  New Doc 2019-04-18 14.18.46-compressed.jpg.jpeg
Views: 10
Size:  67.6 KB

n.b. what do you mean by book?
p.s. I've has less than 4 hours sleep last night as I work full time - which is why I'm asking dumb ass question...so appologies if this make me look stupid.
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ddsizebra
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(Original post by mqb2766)
I meant the model solutions which are given for the questions, no offence was meant to you. We all make mistakes, its how you learn.
what's wrong with the given answers?
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mqb2766
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c) will be similar to the first question in this thread. Its a horizontal force which is pushing the box up. Its slightly greater than the answer to a) so it may even be right ...
(Original post by ddsizebra)
one more (hopefully). How do you question C? I'm assuming it means where I drew the question mark... Name:  New Doc 2019-04-18 14.16.38-compressed.jpg.jpeg
Views: 10
Size:  71.9 KB
Name:  New Doc 2019-04-18 14.18.46-compressed.jpg.jpeg
Views: 10
Size:  67.6 KB

n.b. what do you mean by book?
p.s. I've has less than 4 hours sleep last night as I work full time - which is why I'm asking dumb ass question...so appologies if this make me look stupid.
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mqb2766
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The answers to the question yesterday, the third answer to the moon question, you mentioned another one in yesterdays thread ...
(Original post by ddsizebra)
what's wrong with the given answers?
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