How do you determine the direction of the initial velocity from a v_y vs. v_x graph?

 

To state the obvious, the vertical and horizontal coordinates of a v_y vs. v_x graph are v_y and v_x.� In this simulation, the t=0s data point is marked by a thick black border.� Hence, to determine the two components of the initial velocity, simply read the horizontal and vertical coordinates of the initial data point.�

 

The initial velocity selector is a plot of v_oy vs. v_ox.� On the selector, only one magnitude is possible for each direction.� Hence, knowing the signs of both v_ox and v_oy is sufficient for selecting the initial velocity.�