Hi, I am in experimental physics and having some problems with a question about vacuum technology. They want you to calculate and plot the pressure and pumping speed at the vessel as a function of time. They give you vessel volume, the cylindrical pipe dimensions, and the initial pump speed. I started using this equation; Pt=Ps + (Po-Ps)e^-st/v and conductance which is 1/s=1/so-1/c. If you can get effective pumping speed from this wouldn't it be constant and not changing with time? Thank you.