The total length of a spring when a mass of 20g is hung from its...

JAMB 1983

The total length of a spring when a mass of 20g is hung from its end is 14cm, while its total length is 16cm when a mass of 30g is hung from the same end. Calculate the unstretched length of the spring assuming Hooke's law is obeyed.

A. 9.33cm
B. 10.00cm
C. 10.66cm
D. 12.00cm
E. 15.00cm

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Correct Answer: Option B

Explanation

Let unstretched length = L

e₁ = 14 - L and e₂ = 16 - L

Using, \(\frac{m_1}{e_1}\) = \(\frac{m_2}{e_2}\)

\(\frac{20}{14 - L}\) = \(\frac{30}{16 - L}\)

L = 10cm

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