Rectilinear Motion Question

[hank]

Quick question...

To determine the displacement of a particle, we use the formula
f(x+h) - f(x).

My question is, why do we have to use the h?

Particles travel on a straight line, right?
Why not just use f(x) - f(y)?

Best Regards,

--Hank

 

[stapel]

You can use "f(x + h) - f(x)", and then compute as h goes to 0; or you can use "f(y) - f(x)", and then compute as y goes to x. Either way will do.

Eliz.