You seem to be arguing that an employer can call on an emergency whenever they want to keep an employee working more than 40 hours, but that they can also find busy work during slower periods to make sure they're always hitting 40 regardless. How is that fair or equitable? I guess if they state up front those ridiculous terms, they can ask for it, but don't be surprised to find employees get resentful and less productive the more they're abused.

Sometimes it will take more or less work to get that done. And isn't this how you run your own work life? Are you working right now? Why not? Presumably, you've either finished your needed work, or you know you can get it done later.

Same here. I've scheduled my work week with lots of slack, and generally cut out early on Friday's. Should the people I work for, who have agreed to pay me a certain amount for a certain quantity of work be upset with that?