Our physics expert picks his top-five equations, plus a scheme to supply US power needs with a bucket of baseballs. Thanks, Einstein!

The extension of an elastic object is directly proportional to the force applied. This equation works as long as the elastic limit (the limit of proportionality) is not exceeded. If a spring is ...

Although these restrictions sound severe, the Bernoulli equation is very useful, partly because it is very simple to use and partly because it can give great insight ... surface is less than the ...