The force the original poster refers to is neither lift nor drag as it acts perpendicular to the plane of the balls trajectory which is the plane in which lift and drag are measured. The trajectory "bends" because of this force.
I think there's an argument that
lift is any force in the plane perpendicular to motion. It's conventional to distinguish the component in the direction of an aircraft's yaw axis (
lift) from the component in the direction of its pitch axis (
side force), but the latter is lift in most senses too. But that's terminology, not physics.
And thinking slightly more about the physics, the "differential drag" argument that I put seems to be flawed.
Intuitively, differential drag causes turning: if we deploy the airbrake on one side rather than the other... if we make one tyre of a motor vehicle softer than that on the other side... it will tend to turn.
But fundamentally, Newton's Laws require a force perpendicular to the direction of motion to cause the
turn. Differential drag simply causes
yaw. In the intuitive cases, directional stability pairs that yaw up with a corresponding sideforce and causes the turn.
But for the ball, directional stability doesn't seem relevant. Thus the swing can only be caused by a difference in the mean pressure from one side to the other.
who visits this site for entertainment as well as to learn
Not just you who's learning, RJM.
