1. The problem statement, all variables and given/known data Which of the following phases is capable of permanently withstanding a force perpendicular to its surface? A. Gas B. Liquid C. Solid D. All of the above 2. Relevant equations 3. The attempt at a solution I understand that the answer is D. However, what does it mean to withstand a force? if a gas is in a cylinder with a moveable piston, and then a mass is placed on the piston, the gas would be compressed. So I'm not sure what an example of a gas withstanding a perpendicular force would be. Thanks in advance!