Vacuum Pump and Exponential Pressure Drop · BPhO 2010 #3
Physics · thermodynamics
Problem
A two litre sealed container is filled with air at atmospheric pressure. It is connected to a vacuum pump which can pump air at a flow rate that is proportional to the difference in pressure within the container to the pressure outside. This tells us that the pressure drops exponentially with time. If it takes 20 seconds for the pressure in the container to halve, how long would it take to reduce the pressure in a five litre container from atmospheric pressure to 1/8th of atmospheric pressure
A. 48 s
B. 150 s
C. 200 s
D. 250 s