A piece of wood is floating in water. When the temperature of water rises, the apparent weight of the wood will

One end of a stecl wire is fixed to the ceiling of an elevator moving up with an acceleration $2 \mathrm{~m} / \mathrm{s}^2$ and a load of 10 kg hangs from the other end. If the cross section of the wire is $2 \mathrm{~cm}^2$, then the longitudinal strain in the wire will be ( $\mathrm{g}=10 \mathrm{~m} / \mathrm{s}^2$ and $\mathrm{Y}=2.0 \times 10^{11} \mathrm{~N} / \mathrm{m}^2$ )

Three different liquids are filled in a U-tube as shown in figure. Their densities are $\rho_1, \rho_2$ and $\rho_3$ respectively. From the figure we may conclude that

A piece of granite floats at the interface of mercury and water contained in a beaker as in figure. If the densities of granite, water and mercury are $\rho, \rho_1$ and $\rho_2$ respectively, the ratio of the volume of granite in water to the volume of granite in mercury is