A small sphere of radius `r' falls from rest in a viscous liquid. As a result, heat is produced due to viscous force. The rate of production of heat when the sphere attains its terminal velocity, is proportional to
The power radiated by a black body is P and it radiates maximum energy at wavelength, . If the temperature of the black body is now changed so that it radiates maximum energy at wavelength , the power radiated becomes nP. The value of n is
Two wires are made of the same material and have the same volume, The first wire has cross-sectional area A and the second wire has cross-sectional area 3A. If the length of the first wire is increased by on applying a force F, how much force is needed to stretch the second wire by the same amount ?