Not to mention that F = ma is just a simplification used in entry-level physics classes. The real formula is F = dp/dt, or F = m(dv/dt) + v(dm/dt), which is som

Not to mention that F = ma is just a simplification used in entry-level physics classes. The real formula is F = dp/dt, or F = m(dv/dt) + v(dm/dt), which is sometimes called the "rocket equation" (since rockets burn their fuel to accelerate, they don't have a constant mass). And, he said it's the cornerstone of modern physics; not to be pedantic, but Newton's laws are usually called 'classical physics', while the term 'modern physics' is saved for quantum theory and relativity (check your local university's physics course catalog). Reference: http://en.wikipedia.org/wiki/Force#Newton.27s_second_law http://en.wikipedia.org/wiki/Force#Newton.27s_second_law