When you urinate, you increase pressure in your bladder to produce the flow. for an elephant, gravity does the work. an elephant urinates at a remarkable rate of 0.0060 m3 (a bit over a gallon and a half) per second. assume that the urine exits 1.0 m below the bladder and passes through the urethra, which we can model as a tube of diameter 8.0 cm and length 1.2 m. assume that urine has the same den- sity as water, and that viscosity can be ignored for this flow.