# Finding the instantaneous velocity on a position time graph

by slag1928
Tags: instantaneous, tangent, velocity
 P: 44 It doesn't matter where the line begins or ends, it still has the same slope... So I'd draw a reasonably long line so that both the "rise" ($y_2-y_1$) and "run" ($x_2-x_1$) are biggish numbers, and then calculate their ratio as you suggest. (If they're both big numbers, they're easier to measure precisely so your value for the gradient will be more accurate.)