Explaining expansion calculations with helpful examples

[Grayson Lockwood 2B]

What examples from the class, textbooks, or in real life have been most helpful to understanding the calculations behind expansion work?

[Annaleese Ramos 1E]

I don't have any examples but just remember that the formula for expansion work is w=-p*deltaV and plug in the given values to find the answer.

[ivy knabe 3i]

i had a hard time understanding this too, but what helped were these examples:
A person lifting books from the ground to a shelf does work against gravity.
If we heat a gas, energy is added to the gas molecules. We can see an increase in average kinetic energy of the molecules by measuring how the temperature of the gas increases. As the gas molecules move faster, they also collide with the piston more often. These increasingly frequent collisions transfer energy to the piston and move it against an external pressure, increasing the overall volume of the gas.

This comment on Khanacademy helped me understand the signs "For example if you have a sample of gas in a flexible container and it expands the container to a greater volume than its initial volume, then that results in a positive ΔV. So without the negative sign in the front of the PΔV, the work would be positive. And a positive work means energy went into the system and resulted in a higher amount of energy than when it began. Which doesn't make sense since the gas has to exert force to expand the container and hence had to use up energy to do so. So if it used energy to expand the container, why then would it have gained energy? That's why the negative sign is include to show that the gas was performing work and losing energy to the surroundings."

[Valeria Perez 3J]

I think the best example to really envision expansion work is that of gas expansion in a cylinder with a piston at the top. Think, for instance, about a combustion reaction that causes an increase in gaseous products: As gas is produced, it exerts pressure on the piston, causing it to move upwards, and therefore increasing the volume of the system. The mechanical work being done, in this case, is that of the piston moving upwards against an external pressure. To get the magnitude of that woek, you would employ the equation given by the previous commenter. Hope that makes sense!