Your lawn is twice as large as your neighbor’s lawn. You both start cutting your lawn with the same model, self-propelled lawn mower (requiring the same force) beginning at 9:00am on a Saturday morning. You finish cutting your lawn at 11:00 am. What time will your neighbor finish cutting her lawn if you are equally powerful?

Asheet of steel 1.5 mm thick has nitrogen atmospheres on both sides at 1200oc and is permitted to achieve a steady-state diffusion condition. the diffusion coefficient for nitrogen in steel at this temperature is 6 x 10- 11 m2 /s, and the diffusion flux is found to be 1.2 x 10-7 kg/m2 -s. also, it is known that the concentration of nitrogen in the steel at the high-pressure surface is 4 kg/m3 . how far into the sheet from this high-pressure side will the concentration be 2.0 kg/m3 ? assume a linear concentration profile.