Originally Posted by

**rainer** Hi,

This should probably go in the physics help forum website, but phf seems to have a few glitches that have made it difficult for me to post there.

Anyways, it's really just a simple algebra question that has probably been asked thousands of times:

In Newton's distance formula for a constantly accelerating object, to wit:

$\displaystyle d=v_it+\frac{at^2}{2}$

if $\displaystyle a=(\frac{v_f-v_i}{t})$

so that

$\displaystyle d=v_it+\frac{t^2}{2}(\frac{v_f-v_i}{t})$

why don't the t's cancel??

I.e. why isn't Newton's formula instead:

$\displaystyle d=v_it+\frac{t(v_f-v_i)}{2}$