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TV broadcast antennas are the tallest artificial structures on Earth. In 1987, a

ID: 1583550 • Letter: T

Question

TV broadcast antennas are the tallest artificial structures on Earth. In 1987, a 66.0 kg physicist placed himself and 400 kg of equipment at the top of one 610 m high antenna to perform gravity experiments. By how much (in mm) was the antenna compressed, if we consider it to be equivalent to a steel cylinder 0.130 m in radius? TV broadcast antennas are the tallest artificial structures on Earth. In 1987, a 66.0 kg physicist placed himself and 400 kg of equipment at the top of one 610 m high antenna to perform gravity experiments. By how much (in mm) was the antenna compressed, if we consider it to be equivalent to a steel cylinder 0.130 m in radius?

Explanation / Answer

Young's E = stress / strain = F/A / L/L = FL / AL, so
L = FL / EA

E= young's modulus of steel = 2.10x10^11 N/m2
where F = mg = (66+ 400)kg * 9.8m/s² = 4566.8 N
and A = r² = (0.13m)² = 0.05306 m²

so, L =4566.8×610/(2.10×10^11×0.0531)

L = 2.5×10^-4

L = 0.25 mm...Ans
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