Physics

Problem

A steel square plate of side

40\,\text{cm}

has a circular hole of radius

5\,\text{cm}

at its centre. The plate is cooled from

150\,^{\circ}\text{C}

50\,^{\circ}\text{C}

. Given

\beta_{\text{steel}} = 24\times10^{-6}\,\text{K}^{-1}

, the decrease in the area of the metal (excluding the hole) is closest to a)

2.43\,\text{cm}^2

0.365\,\text{cm}^2

3.65\,\text{cm}^2

7.30\,\text{cm}^2