Physics
Physics
Problem
An open glass tube is immersed in mercury in such a way that a length of 8 cm extends above the mercury level. The open end of the tube is then closed and sealed and the tube is raised vertically up by additional 46 cm. What will be length of the air column above mercury in the tube now? (Atmospheric pressure = 76 cm of Hg) a. 16 cm b. 22 cm c. 38 cm d. 6 cmIntuitive explanation
This problem hinges on understanding how air pressure and volume change together when you trap air and move it. Initially, the trapped air is at atmospheric pressure with a known length; when you raise the tube, atmospheric pressure no longer pushes on that air from below, so the air expands to fill more space. Use Boyle's Law (, or with uniform tube cross-section, ) to find the new air column length, but first figure out the new pressure by considering the mercury column height and what's pushing on the trapped air from outside.
Intuitive explanation
This problem hinges on understanding how air pressure and volume change together when you trap air and move it. Initially, the trapped air is at atmospheric pressure with a known length; when you raise the tube, atmospheric pressure no longer pushes on that air from below, so the air expands to fill more space. Use Boyle's Law (, or with uniform tube cross-section, ) to find the new air column length, but first figure out the new pressure by considering the mercury column height and what's pushing on the trapped air from outside.