Calculating the Specific strength for the rod

In summary, the conversation discusses the possibility of calculating the maximum length and minimum width of a rotating rod placed on top of a skyscraper. The participants wonder about the use of materials such as steel and carbon nanotubes, and inquire about the role of specific strength in determining the maximum length of the rod. They also question whether there is a formula for calculating this length and express curiosity about the topic.
  • #1
Eagle9
238
10
Imagine the skyscraper and the very long rod placed on its top that rotates from horizontal position to upwards.
http://img109.imageshack.us/img109/4817/fhfn.png
I would like to know how is it possible to calculate/ascertain the maximal length and minimal width of the rod made of some certain material, let’s say steel. For example, is it possible to hold the rod with the length of 5 km horizontally (not by hands of course :smile:)? The rod will be broken? What, if I need to hold much longer rod (let’s say 50 km)? Which material should I use? How can I calculate its maximal possible length? As far as I know I need to use the values of Specific strength, right? In Wikipedia I found the article: http://en.wikipedia.org/wiki/Specific_strength and the values for various materials, then what? Let’s assume I am using the carbon nanotubes and I created the rod (not the elastic ribbon like Space Elevator’s cable), how can I calculate its possible maximal length? Is there any formula for this purpose? :smile:
 
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  • #2
Does not anybody know this? :smile:
 

1. How do you calculate the specific strength for a rod?

The specific strength of a rod can be calculated by dividing the breaking strength of the rod by its density. This gives you a measure of the strength of the material per unit of mass.

2. What is the formula for calculating the specific strength?

The formula for calculating the specific strength is specific strength = breaking strength / density.

3. How is specific strength different from strength?

Specific strength takes into account the density of the material, while strength does not. This means that specific strength is a more accurate measure of the material's strength per unit of mass, while strength simply measures the amount of force the material can withstand before breaking.

4. Can specific strength be used to compare different materials?

Yes, specific strength can be used to compare different materials since it takes into account both the strength and density of the material. This allows for a fair comparison between materials of different densities.

5. What are some common units for measuring specific strength?

The most common unit for measuring specific strength is Nm/kg (newton-meter per kilogram). Other units that can be used include lbf/ft³ (pound-force per cubic feet) and MPa·cm³/g (megapascal-cubic centimeter per gram).

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