Explain why someone may have difficulty loosening the wheel nuts/bolts to change a flat tire but find it easier to do so by standing on the end of the wrench. (Application of both math and physics.)
Oh, man, the number of times I’ve used that principle, ucb, since learning it, as a wee young 'un.
I used simple math to figure if the new bookshelves would hold the excessive number of DH’s (at the time) boxed books. I use it to track the degree of inclines in my biking path and project the effort based on the length of the slopes. (Really, to pick the easiest path.) I needed to figure how much dirt to fill the new planter box (large, on wheels) - and how large that box could be before the weight of the dirt meant I couldn’t move the box. Not to mention cost calculations for size and how to cut the wood lengths just so, to avoid buying even one excess piece. Fun thread.
I do the same thing, except I use it to pick the hardest path. 
I thought of you on ny last ride, CF. How I’m a wimp, in comparison.
Yes if you are transferring a cake from a square or oblong pan recipe to a round one, you’d better remember how to calculate the area of a circle!
LF, you’re not a wimp! If you’re out there riding your bike or enjoying other outdoor exercise, you’re not a wimp at all.
No matter how many years of higher math you’ve taken in college, some real-world math problems are incomprehensible…
e.g., airlines’ revised formulas for accumulating frequent flyer miles
http://www.delta.com/content/www/en_US/skymiles/2015-skymiles-program.html?icid=SM_15_announce
It’s now some byzantine algebraic calculation that depends on the cabin class of the ticket, whether you paid full fare, which credit card you used, and what the alignment of Venus and Mars was on the day you booked the ticket.
^^Ha, ha, GMT! And here I thought Delta’s formula for me was just 11 times the cost of my ticket (minus taxes). At least that’s how they’ve done it all year. Who knew that Venus and Mars were part of the formula?