Determine the force that must be applied to a steel reinforcing bar 6 m long and 20 mm in diameter to lengthen it by 2 mm.

univerkov | February 23, 2021 | education

Let’s use Hooke’s law in the following form: F = S * έ * E where S is the cross-sectional area, έ is the elongation έ = Δl / l, E is Young’s modulus (for steel, this value is 2 * 10 ^ 11 n / m ^ 2 ) then:
F = S * Δl / l * E = 20 * 10 ^ -6 * 2 * 10 ^ -3 * 2 * 10 ^ 11/6 = 20 * 2 * 6 * 10 ^ 2/6 = 4000 n = 4 kn

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