vel0Y = effect("Initial Velocity Y")("Slider"); // initial vertical velocity in px/s (positive = down)
vel0X = effect("Initial Velocity X")("Slider"); // initial horizontal velocity in px/s
g_m = effect("Gravity")("Slider"); // gravity in m/s² (e.g. 9.81)
g = g_m * 100; // convert to px/s²
bounce = effect("Bounce %")("Slider") / 100; // elasticity ratio (0–100%)
drag = effect("Air Drag %")("Slider") / 100; // air drag per second (0–100%)
fric = effect("Ground Friction %")("Slider") / 100; // friction applied to horizontal velocity on bounce (0–100%)
floorY = effect("Floor Y")("Slider"); // Y-position of the “ground” in px
startPos = position.valueAtTime(inPoint); // record starting position at layer inPoint
t = time - inPoint;
dt = thisComp.frameDuration;
steps = Math.floor(t / dt);
vx = vel0X;
vy = vel0Y;
x = startPos[0];
y = startPos[1];
for (i = 0; i < steps; i++) {
 vy += g * dt;
 vx *= 1 - drag * dt;
 vy *= 1 - drag * dt;
 x += vx * dt;
 y += vy * dt;
 if (y >= floorY) {
   over = y - floorY;
   y = floorY - over;
   vy = -vy * bounce;
   vx *= 1 - fric;
 }
}
[x, y]