A steel wire of radius $r = 0.5$ mm and length $L = 1$ m is loaded with a weight $W = 200$ N. Young's modulus of steel $Y = 2\times10^{11}$ Pa. The extension $\Delta L$ (in mm) is:

A sphere of radius $r = 1$ mm and density $\rho = 8000$ kg/$m^{3}$ falls in a liquid of density $\sigma = 1200$ kg/$m^{3}$ and viscosity $\eta = 0.1$ Pa·s. The terminal velocity (in cm/s) is (g = 10 m/$s^{2}$):

A copper rod (length 2 m, cross-sectional area $4\times10^{-4}$ $m^{2}$, $K = 400$ W $m^{-1}$$K^{-1}$) connects 200°C source to 0°C sink. The rate of heat flow (in W) is:

The stress in a wire of length 2 m and cross-section $10^{-6}$ $m^{2}$ that is prevented from contracting when cooled by 50°C is ($\alpha = 1.2\times10^{-5}$ $K^{-1}$, $Y = 2\times10^{11}$ Pa):

**Assertion (A):** Stefan-Boltzmann constant $\sigma$ has the same value for all bodies. **Reason (R):** $\sigma$ is a universal constant, but actual power radiated by a real body includes emissivity $\varepsilon$: $P = \varepsilon\sigma AT^4$.