A pendulum clock (fitted with a small heavy bob that is connected with a metal rod) is $5\, seconds$ fast each day at a temperature of $15\,^oC$ and $10\,seconds$ slow at a temperature of $30\,^oC$. The temperature at which it is designed to give correct time, is ........ $^oC$

What is thermal expansion ? Write only its types.

A solid ball is completely immersed in a liquid. The coefficients of volume expansion of the ball and liquid are $3 × 10^{-6}$ and $8 × 10^{-6} per ^o C$ respectively. The percentage change in upthrust when the temperature is increased by $100 ^o C$ is ....... $\%$

A beaker is filled with water at $4\,^oC$. At one time the temperature is increased by few degrees above $4\,^oC$ and at another time it is decreased by a few degrees below $4\,^oC$. One shall observe that:

The gap between any two rails, each of length $l$ laid on a railway track equal $x$ at $27\,^oC$ . When the temperature rises to $40\,^oC$ , the gap close up. The coefficient of linear expansion of the material of the rail is $\alpha $ . The length $l$ of a rail at $27\,^oC$ will be

A rod of length $2m$ rests on smooth horizontal floor. If the rod is heated from $0^o C$ to $20^o C$. Find the longitudinal strain developed? $(\alpha = 5 × 10^{-5}/^o C)$