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WAEC Physics 2013 Paper

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Question : 12

Total: 46

A body of mass 11kg is suspended from a ceiling fan by an aluminum wire of length 2m and diameter 2mm. Calculate the elastic energy stored in the wire [Young's modulus of aluminum is 7.0 x

10^{10}\mathrm{Nm}^{-2}

\mathrm{s}^{-2}

\pi

= 3.142]`

1.1 x 10^-1J
5.5 x 10^-2J
1.1 x 10^-4J
5.5 x 10^-8J

Solution:

e = $\frac{4FI}{Y \pi d^2} = \frac{4 \times 11 \times 10 \times 2}{7 \times 10^{10} \times 3.14 (2 \times 10^{-3})^2}$

= 0.001m

E =

\frac{1}{2} \mathrm{Fe} = \frac{1}{2} \times 110 \times 0.001

= 5.5 x

10^{-2}

J

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