A supertrain of proper length 200 m travels at a speed of 0.9 times the speed of light (relative to the tunnel) as it passes through a tunnel having proper length 80 m. In the reference frame of the tunnel, how much longer is the train than the tunnel

Carbon is allowed to diffuse through a steel plate 15 mm thick. the concentrations of carbon at the two faces are 0.65 and 0.30 kg c/m^3 fe, which are maintained constant. if the preexponential and activation energy are 6.2 x 10-7 m2 /s and 80,000 j/mol, respectively, compute the temperature at which the diffusion flux is 1.43 x 10^-9 kg/m^2 -s.