For an object that has positive constant acceleration what does the speed vs time graph look like

The graph look like a line with positive slope and y-intercept equal to zero.

Explanation:

Acceleration (a) is defined as follows:

a = v/t

where v refers to speed and t refers to time.

Isolating speed in the equation we get:

v = a*t

With a positive constant acceleration, this is the equation of a line with v as dependent variable, t as independent variable, and a as positive slope, which passes through coordinate (0, 0).