I've got a ridiculously basic question that I'm sure has an equally absurd simple answer…
I'm animating a 10 second clip of a Photoshoped ball flying from the distant left of the frame where it is to exit the right side. The technique being used is Basic 101: image scale reduced at the beginning and enlarged at the endpoint, with positions keyframed at the start and finish.
My problem is that the ball starts off fast, but then slows to a death-defying creep as it grows enormous and rolls off screen. Never did well in high school Physics, but I'm preety sure the motion characteristics need to be the other way around: appears slow, then excellerates. I've played around with all of the curve functions, but can't get this bugger to fly right.
It sounds like you want it to look as if it's getting closer to the camera as it moves across instead of just getting bigger. It's less of a physics thing and more of a visual thing and how look like they move closer to the camera. You are correct though, if it's supposed to be bigger because it's closer to the camera, then it should also be seem to be moving faster.
The quick solution is just to make it 3d and have it start far away from the camera and move closer and to the right until it's basically just to the right of the camera off screen. You could also right click on the position and scale keyframes, go to Keyframe Assisstant>Exponential Scale.