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SalivaKB
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Homework Statement
Suppose you have a very long steel bar, with a regular pentagonal cross-section where each side of the pentagon is 2 cm in length. This bar will be suspended vertically over a very deep chasm. At the bottom end of the steel bar, there is a spherical steel weight with a diameter of 50 cm. Going up the bar, at every 3 meter increment, there is a spherical steel weight with a diameter of 30cm.
If the density of the steel is exactly 7.8 g/cm3, the steel can withstand a tensile stress of 400 MPa, and gravity is 9.81m/s2, what is the maximum possible length, in metres, that the bar can extend without breaking? Round down to the nearest metre, submit only a number (with no additional or extraneous information), and disregard any deformation of the bar or any other forces acting on the bar.
Homework Equations
P=m/V
Acircle= Pie (R)2
I seem to not remember the formula for this, such as the area for the regular pentagon. My son brought this up to me and I told him I will do my best but I hit a stump.