UPDATE PHYSICS- Spin

When ever a body or object moves through air, it experiences an aerodynamic drag force opposing its motion. Under certain conditions a second type of force aerodynamic lift, also will act on the object. Lift force, however, is always directed perpendicular to the oncoming flow, not parallel to the flow as is drag force.
In sport, lift force acts on bodies and objects whose shapes or positions influence the pattern of air flow around them. Lift force also acts on a projectile whose spin influences the pattern of air flow around it.
To understand how aerodynamic lift force is generated, air flow relative to the moving object must be examined. The nature of air flow past the airfoil demonstrates the concept of lift force. As air flows past the airfoil, it flows faster over the upper curved surface than underneath the object. Such a flow velocity difference existing between opposites sides of an object causes a pressure difference between the two sides. The relationship between flow velocity and pressure is an inverse one, and is expressed in Bernoulli's principle. "Where the flow velocity is fast, the pressure is low; where the flow velocity is slow, the pressure is high." The existing pressure difference causes the wing shape to experience a force directed from the region of higher pressure underneath to the region of lower pressure on top. The direction of lift force is perpendicular to the flow direction past the object, whereas the drag force is directed parallel to the flow direction.

ANGLES
Angle of attack... The best angle of attack for producing the greatest lift force with the least drag force depends on the shape of the object and the velocity of the air flow. The angle of attack changes throughout the flight path as the relative air flow direction changes as the object ascends then descends.
The projection angle is the angle of the center of gravity's (CG) instantaneous velocity vector at release, measured from the horizontal. After release, the instantaneous velocity of the angle at any instant depicts its line of flight. The Attitude angle is the angle formed between the main plane of the object and the horizontal ground. It represents the orientation of the implement in space and is the angle that is most obvious to the observer.
Aerodynamic lift is created by a force acting perpendicular to the flow direction past a projectile that is inclined to flow at some angle of attack so as to create the necessary pressure difference between two sides of the object. Aerodynamic lift is also created on objects projected with spin. The lift force generated by a spinning object traveling through the air is responsible for the deviation in the flight path from that which is expected, such as in a curve ball. Such a lift force results from a pressure difference between opposites sides of the ball, and this pressure difference depends on the flow-velocity difference, in accordance with Bernoulli's principle. This particular mechanism by which lift force is generated on a spinning ball is called the Magnus effect, and the force of lift is sometimes referred to as Magnus Force.
To gain an understanding of this force, consider the motion of a ball thrown with top spin. As the ball spins, it carries a thin layer of air, the boundary layer, around with it. The ball's forward linear motion creates an air flow backward past the ball surface. This forward-moving top boundary layer encounters the backward flow of air past the ball. The mixing of these oppositely directed air layers results in decreased flow velocity relative to the top surface of the ball and a consequent increase in pressure. On the bottom side, the boundary layer is moving backward with the ball surface due to its spin, and the backward flow of air past the moving ball is reinforced, thus creating a lower pressure region on the bottom. The result is a net force on the ball directed downward from the region of higher pressure on the top to the lower-pressure region on the bottom. The effect of this force is to cause the ball to accelerate downward at a faster rate than it would be accelerated by gravity alone. The net force acting downward on the ball is its weight plus the downward force of lift. Thus, top spinning balls are forced to the ground sooner, or faster, than balls with either no spin or other spin directions. For this reason, top spin is used for projecting balls that must fall within a court boundary as in a tennis, table tennis, and volleyball.
A ball thrown with top spin experiences a slower air flow velocity, and thus higher pressure on the top surface and it experiences a faster air, flow velocity and thus lower pressure on the bottom surface. A downward directed Magnus (lift) force is produced on the ball as a result of the pressure difference.

The Magnus force on a top spinning ball has vertical and horizontal components that affects the flight of the ball differently at different points in its path. Note that the relative flow changes directions as the ball changes direction.

During the descending portion of flight, the air flow is directed backward and upward past the ball, and the Magnus force is therefore downward and backward. This change in direction of the air flow past the object is what causes the ball to take on a greater curve downward toward the end of its flight. The downward component continues to augment gravity's pull accelerating the ball downward at a greater magnitude than would gravity itself. The backward component of this Magnus force resists the forward motion of the ball, causing it to fall at a steep angle of approach to the ground. It is readily apparent why top spin is an effective mechanism for restricting the horizontal distance of a ball that is traveling at a relatively high velocity; if the ball were projected with the desired horizontal velocity without top spin, it would travel too far before hitting the ground. Thus a tennis player able to impart top spin to the ball can project it with a higher velocity and still keep it in bounds. A top spinning ball also strikes the ground at a more vertical angle than a non spinning ball, due to the greater deviation downward near the end of its flight.
The Magnus effect is evident also on a bottom spinning balls. The lift force is directed upward from the high pressure region below the ball toward the low pressure zone above. Bottom spin is used to project the ball for the purpose of maximizing the horizontal distance or time in the air or for accurate placements, as in golf, tennis, and soccer, because the upward Magnus force causes the ball to experience less acceleration downward due to gravity's pull a ball with another type of spin. The net downward force experienced by a bottom spinning ball spinning ball is its weight minus the upward Magnus force. The Magnus force acts perpendicular to the flow direction past the ball. During the ascent an upward component of force tends to elevate the ball and a backward component increases the resistance against its forward motion. Near the peak of the path, the air flow is horizontal, and the Magnus force is entirely upward. During the descent, the flow direction past the ball is such that the Magnus force is directed upward and inward. The upward component still resists the normal downward acceleration due to gravity, and the forward component acts to provide a forward propulsive force on the ball. The flight of a ball with back spin is prolonged due to the lift force. The downward acceleration due to gravity acts over a greater period of time so that the ball strikes the ground at a more vertical angle than a ball with no spin, but not a steeply as a ball with top spin. The backspin on impact also tends to cause the ball to rebound at a steeple angle, This angle depends on the angle at which the ball strikes and the amount of skidding that occurs between the ball and rebound surface.
Because of the angle of the club face and the patter of the swing, a golf ball hit for distance and hit straight usually has a backspin imparted to it. Consequently the ball is lifted toward the tail end of its flight. Because the lift force acts to keep the ball in the air longer, there is less need to project it with a larger vertical velocity component, which also serves to keep the ball in the air longer. Therefore long shots such as drives should be projected with more horizontal velocity on club impact than shots with middle or short irons