Question

On heating, a uniform metallic cylinder length increases by 3%. The area of a cross-section of its base will increase by:

• A. 1.5%
• B. 3%
• C. 9%
• D. 6%

Answer 1

The correct option is C 9%

$A=\pi r^2\delta A=3\pi r\times \delta r=\frac{3A\delta r}{r}\frac{\delta A}{A}=3\times \frac{\delta r}{r}$

Given: $\frac{\delta r}{r}=3\%$

$\therefore \frac{\delta A}{A}=3\times 3\%=9\%$