+251 Hi there,
Having a bit of a problem with this one; hope you can help.
My lecturer did this problem in kN/mm while I like to use base units: N/m
We need to find dn.
Here is the lectuers final equation to solve for dn:
dn = 61.2mm
Note; the units for the values are as follows:
6.85 = kN
132 = unitless
40 = mm
465 = kN
dn = mm
Here's my final equation:
dn=0.06785m
I think the problem is lies with finding the term 6.85dn or 6852300dn
Here is the lecturers equation to find 6.85dn
Note; the units for the values are as follows:
0.802 = unitless
32 = MPa
300 = mm
0.89 = unitless
1000 = unitless
Where as my Cc is as follows:
Any ideas?
I've run it by the lecturer but they didn't know why either. They put it down to a rounding error.
+37153 How do you go from 6.85 dn to 6852300 dn
shouldn't it be 6852.3 dn ?
+251 sorry, I wrote in the *10^-3 at the last second.
I've used 6852300 as Newtons
+37153 I am referring to your first equation.....it starts as 6.85 kn which is 6852.3 N not 6852300 N
Wait....now I see you converted dn to m from mm which would make it 6852300.....
looking some more....
Wait...again.....when you converted dn to m you MULTIPLIED by 1000.....you should DIVIDE by 1000
Then I get - 6.8523 d^2 + 464868 d + 5.28 = 0 resulting in dn = 67841.2
+251 yeah I don't understand how it's 6.85 either. I was hoping someone could shed some light.
The third image shows how the 6.85dn was calculated
+37153 I think the problem is lies with finding the term 6.85dn or 6852300dn
6.8523 kn dn when dn is in mm
when you convert to m and N
this just equals 6.8523 N dn
+37153 I don't think we are talking about the same things:
you have:
Here's my final equation:
465000 = 132/d (d- .04) + 6852300
This should be
465000 = 132 (d-.04) + 6.8523
solving for d n = 67841.2 N = 67.841 kn
then cc = .802 x 32 x 300 x .89 dn / 1000 = 464.86 mm
