When the temperature of a metal wire is increased from $0^{\circ} \,C$ to $10^{\circ} \,C$,its length increases by $0.02 \%$. The percentage change in its mass density will be closest to: (in $\%$)

$A$ brass rod of length $50\; cm$ and diameter $3.0\; mm$ is joined to a steel rod of the same length and diameter. What is the change in length of the combined rod at $250\; ^{\circ}C$,if the original lengths are at $40.0\; ^{\circ}C$? Is there a 'thermal stress' developed at the junction? The ends of the rod are free to expand. (Coefficient of linear expansion of brass $= 2.0 \times 10^{-5}\; K^{-1}$,steel $= 1.2 \times 10^{-5}\; K^{-1}$)

$A$ metal rod of silver at $0^{\circ}C$ is heated to $100^{\circ}C$. Its length increases by $0.19\, cm$. If the original length of the rod is $100\, cm$,the coefficient of cubical expansion of the silver rod is:

$A$ steel tape of $300 \,cm$ length is graduated at $27^{\circ} C$. The length of a steel rod measured using the tape is found to be $110 \,cm$ at $50^{\circ} C$. The actual length of the steel rod at $50^{\circ} C$ is $(\alpha_{\text{steel}} = 1.2 \times 10^{-5} \,K^{-1})$. (in $\,cm$)

$A$ clock which keeps correct time at $20^{\circ} C$, is subjected to $40^{\circ} C$. If the coefficient of linear expansion of the pendulum is $12 \times 10^{-6} /{ }^{\circ} C$, how much time will it gain or lose per day?

Solids expand on heating because