The work done to stretch an elastic string by 40cm is 20 Joules
Hooke law states that the force (F) applied to a spring is directly proportional to the extension (e).
F ∝ e
F = ke
k is the constant
Given that a force of 10N produces an extension of 4cm, hence:
F = ke
10 = k(4)
k = 2.5 N/cm
For an extension of 40cm, the work done is:
Work done = (1/2)ke²
Work done = (1/2)(2.5 N/cm)(40 cm)² = 2000Ncm = 20 Nm
Work done = 20 Joules
The work done to stretch an elastic string by 40cm is 20 Joules
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