Algodoo

I decided to use the thing I claimed worled like a muscle to bascially build one. This is what muscles do at a microscopic scale, but you can assume we jumbo-sized one of those muscle cells... to the size of a house.

Anyway, watch as the muscle exerts an estimated 800 pounds of force on a disadvantageous lever to lift over 100 pounds. It's nearly magical how much force real muscles can exert, especially considering how inefficient their power is used. Here's an interesting fact, speaking of muscles: Your achilles tendon can withstand about 1100 pounds of force!

W (tap repeatedly) to flex muscle