A question regarding columns and GNm and MNm

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In summary, the conversation is about determining the minimum length of a column at which buckling is likely to occur. The person is given a Young's modulus of 200 GNm-2 and a yield stress of 140 MNm-2. They are trying to convert the units to be able to use an equation, but are unsure of the correct conversion. Another person provides helpful tips on correctly writing units according to international standards and clarifies the conversion from GNm-2 to MPa. The person expresses their gratitude and admits to struggling with SI units and powers of 10 due to lack of recent use.
  • #1
Harrison01
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Ok i have a question regarding columns and it goes a bit like this,

What is the minimum length of the column at which buckling is
likely to occur?

They have given me the youngs modulus of 200GNm-2 (200,000,000,000 Nm) and a yield stress of 140MNm-2 (140,000,000Nm).

For working out my equation I'm trying to get the figures in the same unit. So 200GNm-2 to MNm

Do i divide the 200 by 1 million to give me 0.0002Nm and then multiply it by 100,000 to give me 200, but this then can't be right?

where am i going wrong folks...
 
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Harrison01: (1) MN*m^-2 is called MPa. Always use the correct, special name for a unit. E.g., 140 MPa, not 140 MN*m^-2. See the international standard for writing units (ISO 31-0).

(2) Always leave a space between a numeric value and its following unit symbol. E.g., 140 MPa, not 140MPa.

(3) Two unit symbols multiplied together cannot be written together, and must be separated by an asterisk or a space. E.g., N*m or N m, not Nm.

(4) The international standard says you can write digits of long numbers in groups of three, separated by spaces, not commas. E.g., 140 000 000 Pa, not 140,000,000 Pa.

(5) 1 GPa = 1000 MPa. Therefore, 200 GPa = 200 000 MPa.

(6) Other valid ways to write 200 000 MPa include, e.g., 200*10^3 MPa, or 200e3 MPa. Another way to write, e.g., -0.3 m^-4 is -0.3*10^-12 mm^-4, or -0.3e-12 mm^-4.
 
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  • #3
Cheers NVN, that's starting to make things a lot clearer for me now...

I think what threw me is that in the question i was given, all the figures were GN m and MN m and the example i was given the figures were in MPa and GPa..

Finding getting used to all these SI units and powers of 10 a struggle as its been so long since last using it..
 

1. What is the difference between GNm and MNm?

The main difference between GNm (Giganeuton meters) and MNm (Meganewton meters) is the unit of measurement. GNm is a unit of torque, while MNm is a unit of force multiplied by distance, which is equal to work or energy.

2. How do you convert GNm to MNm?

To convert GNm to MNm, you can use the conversion factor of 1 GNm = 1000 MNm. This means that you need to multiply the value in GNm by 1000 to get the equivalent value in MNm.

3. Why are GNm and MNm important in columns?

GNm and MNm are important in columns because they are commonly used as measures of the strength and stability of a column. These units represent the maximum amount of torque or force that a column can withstand before buckling or failing.

4. How is GNm or MNm calculated for a column?

The GNm or MNm value for a column is calculated by multiplying the maximum force or torque acting on the column by the length of the column. This calculation takes into account the material properties and dimensions of the column to determine its strength and stability.

5. Can GNm and MNm be used interchangeably in column calculations?

No, GNm and MNm cannot be used interchangeably in column calculations because they represent different units of measurement. Using the wrong unit can result in incorrect calculations and lead to safety hazards or structural failures.

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