Two rods of different materials having coefficient of linear expansion $\alpha_1$and $\alpha_2$ and  Young's modulii $Y_1$ and $Y_2$ respectively are fixed between two rigid massive walls. The rods are heated such that they undergo the same increase in temperature. There is no bending of rods. If  $\alpha_1:\alpha_2= 2 : 3$, the thermal stress developed in two rods are equal provided $Y_1 : Y_2$ is equal to

The scale on a steel metre stick is calibrated at $20^o\,C$.The error in the reading of $50\,cm$ at $30^o\,C$ is: (take linear expansion coefficient of steel $= 1.0 \times 10^{-5} /  ^oC)$

Give name of substance that contracts with increase in temperature.

An external pressure $P$ is applied on a cube at $0^o C$ so that it is equally compressed from all sides. $K$ is the bulk modulus of the material of the cube and a is its coefficient of linear expansion. Suppose we want to bring the cube to its original size by heating. The temperature should be raised by

Surface of the lake is at $2°C$. Find the temperature of the bottom of the lake........ $^oC$

Expansion during heating