If two rods of lengths $L$ and $2L$,having coefficients of linear expansion $\alpha$ and $2\alpha$ respectively are connected end-to-end,then find the average coefficient of linear expansion of the composite rod.

The coefficient of linear expansion depends on

Steel rails are laid with gaps to allow for thermal expansion. Each track is $10 \ m$ long,when laid at a temperature of $17^{\circ} C$. The maximum temperature that can be reached is $45^{\circ} C$. The gap to be kept between the two segments of the railway track is $(\alpha_{\text{steel}} = 1.3 \times 10^{-5} /^{\circ} C)$. (in $mm$)

$A$ $1$ litre glass flask contains some mercury. It is found that at different temperatures,the volume of air inside the flask remains the same. What is the volume of mercury in this flask in $cc$ if the coefficient of linear expansion of glass is $9 \times 10^{-6} /^{\circ}C$ and the coefficient of volume expansion of mercury is $1.8 \times 10^{-4} /^{\circ}C$?

$A$ solid expands upon heating because

The area of a circular copper coin increases by $0.4 \%$ when its temperature is raised by $100^{\circ} C$. The coefficient of linear expansion of the coin is: