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November 11th, 2011, 01:06 AM   #1
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can check this Q in moment

Hi


-------------------------

answer number 10 )

clockwise (-)
ant-colc wise (+)

Moment of A
30(0) + 15 (4) + 25 (2)
Ma = 170 Nm

Moment of B = 30(2) + 15(0) + 25(2)
Ma = 110
Moment of c
= -30(2) - 15(4) - 25(0)
Mc = -120 Nm

----------

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November 11th, 2011, 11:35 AM   #2
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You have the right method, but are making careless errors. Also, write "moment about A" instead of "moment of A".
The diagram for problem 10 doesn't show the exact angle for the 15N force, so I'll assume that it is 45°.

10. Moment about A = 30(2)Nm + 15(2?2)Nm + 25(2)Nm = (110 + 30?2)Nm, which you can approximate if you like.
      Moment about B = 30(2)Nm + 15(0)Nm + 25(-2)Nm = 10Nm exactly.
      Moment about C = 30(-2)Nm + 15(-2?2)Nm + 25(-2)Nm = -(110 + 30?2)Nm, which you can approximate if you like.

Do you understand why the signs I've used are correct?
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November 11th, 2011, 11:45 AM   #3
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Re: can check this Q in moment

Hi , why you are divide by root of 2 15(2?2)Nm?

and if the distance for example 4 it should be 15([color=#FF0000]4[/color]?2)Nm


Note : m= Fx r
r = perpendicular distance between the point or axis about which the moment is required and the line of action of the force
,,, thanks again.
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November 11th, 2011, 11:56 AM   #4
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I didn't divide. I multiplied by sec(45°), which is ?2.
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November 11th, 2011, 11:58 AM   #5
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Re: can check this Q in moment

Note : m= Fx r
r = perpendicular distance between the point or axis about which the moment is required and the line of action of the force

the 15X 2

not 15X 2?2)

Is there angle ... ?
??
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November 11th, 2011, 12:06 PM   #6
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I don't understand what you are asking. The 15N force is shown at an angle not specified very clearly. I assumed that the angle is 45°, so that the line of action passes through B and the perpendicular direction is the same as the direction of CA.
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November 11th, 2011, 12:12 PM   #7
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Re: can check this Q in moment

Ac = root(4^2 + 4^2) = 5.6
Ac = 5.6

then for moment of A of 15
15(2.8 )Nm

Is correct ?
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November 11th, 2011, 12:22 PM   #8
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Re: can check this Q in moment

okkkkkk now ... It's same ....


Ok please see here ,,,

viewtopic.php?f=43&t=24781
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November 11th, 2011, 12:41 PM   #9
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How many significant figures are you supposed to use in approximate values?

I suggest you redo problem 11, taking more care over signs and remembering to give the moment about D.
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November 11th, 2011, 01:05 PM   #10
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Re: can check this Q in moment

Number 11 ) moment of A the force 25 Negative (-)
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