The position of a 3.0 kg mass is given by x=(2t^3−3t^2) m, where t is in seconds.
what is the net horizontal force on the mass at t=0s?
what is the net horizontal force on the mass at t=1s?

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.