bigr
Well-known member
- Joined
- Nov 27, 2001
- Posts
- 142
We studied this in my fluid dynamics class in college.
corky is on the right track, however the conclusion is wrong.
and enigma is essentially right. the curve ball you see on TV is for the most part an optical illusion. however there are aerodynamic forces at work.
a better illustration of a curve ball is the "tennis ball".
what causes a ball to "curve" is the interaction of the "boundary layer" on the ball interacting with the relative wind.
if you have ever hit a tennis ball with back spin then you notice that the ball will "float" and probably be out of bounds. however, for those of you old enough to remember Bjorn Borg and Guilermo Villas, they both hit the tennis ball with tremendous "top spin". this made the ball "dive" into the court.
why does this happen?
this happens because of the boundary layer of air around the ball.
what is the boundary layer? it is a microscopic thin layer of air that "attaches" to the ball. this also happens to an airfoil and causes drag. engineers have been trying to reduce this for years and i won't go into it.
the boundary layer spins with the ball. think of the boundary layer as a microscopic layer of air that adhears to the ball and spins with it. thus for a tennis ball with top spin, this creates an interaction between the boundary layer of air and the relative air that the ball flys thru. this creates a greater pressure differential at the top of the ball (forward of top dead center of the ball). at the bottom of the ball the boundary layer has less relative velocity with the "relative wind" of the ball flying thru the air. thus this is a lower pressure area and the tennis ball is "pushed downward" if it has top spin. this is an aerodynamic force and has nothing to do with rotational momentum or gyroscopic forces.
therefore, a curve ball thrown that rotates clockwise (looking down) will curve to the right.
check out "aerodynamics for naval aviators". it explains this in terms of airfoils.
corky is on the right track, however the conclusion is wrong.
and enigma is essentially right. the curve ball you see on TV is for the most part an optical illusion. however there are aerodynamic forces at work.
a better illustration of a curve ball is the "tennis ball".
what causes a ball to "curve" is the interaction of the "boundary layer" on the ball interacting with the relative wind.
if you have ever hit a tennis ball with back spin then you notice that the ball will "float" and probably be out of bounds. however, for those of you old enough to remember Bjorn Borg and Guilermo Villas, they both hit the tennis ball with tremendous "top spin". this made the ball "dive" into the court.
why does this happen?
this happens because of the boundary layer of air around the ball.
what is the boundary layer? it is a microscopic thin layer of air that "attaches" to the ball. this also happens to an airfoil and causes drag. engineers have been trying to reduce this for years and i won't go into it.
the boundary layer spins with the ball. think of the boundary layer as a microscopic layer of air that adhears to the ball and spins with it. thus for a tennis ball with top spin, this creates an interaction between the boundary layer of air and the relative air that the ball flys thru. this creates a greater pressure differential at the top of the ball (forward of top dead center of the ball). at the bottom of the ball the boundary layer has less relative velocity with the "relative wind" of the ball flying thru the air. thus this is a lower pressure area and the tennis ball is "pushed downward" if it has top spin. this is an aerodynamic force and has nothing to do with rotational momentum or gyroscopic forces.
therefore, a curve ball thrown that rotates clockwise (looking down) will curve to the right.
check out "aerodynamics for naval aviators". it explains this in terms of airfoils.