149. Please explain what "lift" is.
Suppose that a horizontal wind is approaching a smooth, stationary ball from the right. The ball will experience a drag force that pushes it toward the left. We call it a drag force because it acts to slow the ball's motion through the air—in other words because it pushes the ball directly downwind. But if the ball isn't uniform or if the ball is spinning, it may experience a force that isn't directly downwind. If the ball experiences an aerodynamic force (a force due to the motion of the wind near its surface) that pushes it to the side, or that pushes it up or down, then it is experiencing a lift force. This lift force isn't necessary up...it's just to the side—at right angles to the downwind direction.