So, how does a frisbee fly?

But wait a minute. A good frisbee thrower can make a frisbee rise
straight up (like a golf ball does). The frisbee may take one path for
awhile but then starts heading up, just like a properly hit golf ball
(although not mine golf balls ). The golf ball is well understood to
rise as a result of its backward spin and low pressure on top (B).
Anyone who claims that a golf ball just follows its original path has
certainly never seen one properly hit.

-Robert

"Robert M. Gary" wrote in message
ups.com...
But wait a minute. A good frisbee thrower can make a frisbee rise
straight up (like a golf ball does). The frisbee may take one path for
awhile but then starts heading up, just like a properly hit golf ball

Yes. As I said in a different post, there are subtle aerodynamic effects
that can be used to affect the exact flight path of the frisbee. Release
attitude (pitch and roll), initial flight path, rotation speed, even impact
(intentional or otherwise ) with some object or surface mid-flight, these
all have small-but-interesting-and-useful effects on the exact course the
frisbee follows.

But those are very minor, the frisbee at all times is following basic rules
of inertia and lift (without the radical changes in configuration that CJ's
post suggests), and the original question was simply how does the frisbee
*fly*. That is, why is it possible to throw a frisbee and have it maintain
any stable path, and remain aloft longer than a thrown rock would.

Pete

"Peter Duniho" wrote

Yes. As I said in a different post, there are subtle aerodynamic effects
that can be used to affect the exact flight path of the frisbee. Release
attitude (pitch and roll), initial flight path, rotation speed, even
impact (intentional or otherwise ) with some object or surface
mid-flight, these all have small-but-interesting-and-useful effects on the
exact course the frisbee follows.

A large factor is also the gyroscopic affects (effects?) resulting from the
change in plane of rotation, like the spinning bicycle wheel being held by
the person on the turntable.

That is why (for a right handed person, throwing with the standard clockwise
rotation) the release position for a straight throw, is with the side
opposite from the hand to be held lower than the side the hand is holding.
--
Jim in NC

Robert M. Gary wrote:
But wait a minute. A good frisbee thrower can make a frisbee rise
straight up (like a golf ball does). The frisbee may take one path for
awhile but then starts heading up, just like a properly hit golf ball
(although not mine golf balls ). The golf ball is well understood to
rise as a result of its backward spin and low pressure on top (B).
Anyone who claims that a golf ball just follows its original path has
certainly never seen one properly hit.

I haven't seen an analysis of a golf ball, but I saw an analysis a while
ago on a baseball. I think it may have been in Popular Mechanics, but
I'm not sure of that. The claim was that a baseball could be thrown so
as to rise (I forgot which type of pitch it is called) on its way to the
plate. The article pretty clearly debunked this myth. The spin
imparted to the ball can make it sink a little less slowly than a strict
ballistic trajectory, but the RPM required to actually make the ball
rise was something simply unattainable by a human.

I suspect the same is true of a golf ball (I'm a golfer, but not a
terribly good one). I've watched a number of balls hit by amatuers and
pros and I've never seen one rise above the launch trajectory. The
backspin will certainly make the trajectory much flatter than a
ballistic trajectory, but I don't think the ball will rise above a
tangent line to the path leaving the club face.


Matt

Matt Whiting wrote:
Robert M. Gary wrote:
I suspect the same is true of a golf ball (I'm a golfer, but not a
terribly good one). I've watched a number of balls hit by amatuers and
pros and I've never seen one rise above the launch trajectory. The
backspin will certainly make the trajectory much flatter than a
ballistic trajectory, but I don't think the ball will rise above a
tangent line to the path leaving the club face.

Golf balls clearly have lift and Cl is one of the criteria used when
evaluating ball standards. Here is a pdf describing some of the
formuals used and how the coefficient of lift for different balls
effects flight.
http://www.usga.org/equipment/techni...ublication.pdf

"It has been shown (Bearman, Harvey, 1976) that the two aerodynamic
coefficients, CD
and CL, are related to the dimensionless Reynolds number (Re) and spin
ratio (W)."

Spin is one component that determins the lift produced by the ball.

Here is an article from Cislunar Aerospace, Inc
http://wings.avkids.com/Book/Sports/...d/golf-01.html

"How a Golf Ball produces Lift

Lift is another aerodynamic force which affects the flight of a golf
ball. This idea might sound a little odd, but given the proper spin a
golf ball can produce lift. At first, golfers thought all spin was
detrimental (not good). However, in 1877, British scientist P.G. Tait
learned that a ball, driven with a "backspin" (the top of the ball
turning back toward the golfer) actually produces lift.

The dimples also increase lift. Remember, dimples help keep the flow
attached to the sphere. The dimples also cause the flow to be "focused"
into the flow of the wake. In this figure, the smoke shows the flow
pattern around a spinning golf ball. The flow is moving from left to
right and the ball is spinning in a counter-clockwise direction. The
wake is being forced downwards. This downward movement of the wake
means that a lifting force is being applied to the golf ball.
"

-Robert

Robert M. Gary wrote:
Matt Whiting wrote:

Robert M. Gary wrote:
I suspect the same is true of a golf ball (I'm a golfer, but not a
terribly good one). I've watched a number of balls hit by amatuers and
pros and I've never seen one rise above the launch trajectory. The
backspin will certainly make the trajectory much flatter than a
ballistic trajectory, but I don't think the ball will rise above a
tangent line to the path leaving the club face.


Golf balls clearly have lift and Cl is one of the criteria used when
evaluating ball standards. Here is a pdf describing some of the
formuals used and how the coefficient of lift for different balls
effects flight.
http://www.usga.org/equipment/techni...ublication.pdf

I never disputed that golf balls have lift. I simply said I don't think
they will rise above the launch line as was suggested.

The lift will cause them to descend more slowly that they would due to
ballistics alone, but that is far different than saying they will rise
upwards above the launch path.


Matt

Matt Whiting wrote:
:
I never disputed that golf balls have lift. I simply said I don't think
they will rise above the launch line as was suggested.

The lift will cause them to descend more slowly that they would due to
ballistics alone, but that is far different than saying they will rise
upwards above the launch path.

That is not what I've observed. When watching professional golfers hit
balls they appear to travel a traditional trajectory (often call the
"cannon" route) for the first couple hundred feet and then take a
noticable up path when they should start to sink. That up path seems
quite dramatic to me. Its often called the "second wind". That's just
my observation.

-Robert

Robert M. Gary wrote:
Matt Whiting wrote:
:

I never disputed that golf balls have lift. I simply said I don't think
they will rise above the launch line as was suggested.

The lift will cause them to descend more slowly that they would due to
ballistics alone, but that is far different than saying they will rise
upwards above the launch path.


That is not what I've observed. When watching professional golfers hit
balls they appear to travel a traditional trajectory (often call the
"cannon" route) for the first couple hundred feet and then take a
noticable up path when they should start to sink. That up path seems
quite dramatic to me. Its often called the "second wind". That's just
my observation.

That is the same thing people claimed about baseballs, but it turned out
to be a combination of an optical illusion (the mound being higher than
the plate) and people's mind expecting the ball to drop more quickly
than it did and then perceiving this as the ball rising, when it fact it
was simply dropping at a slower rate.

I was watching golf this past weekend and they had several side aerial
shots of the drives. It was pretty easy to see the trajectory of the
ball from the lift or whatever they were filming from as the height was
about the same level as the apex of the drive. The ball was clearly
dropping away from the path of launch when viewed from the side at an
elevated position.

If you get a chance to see these sorts of shots on TV in the future,
look closely and I think you'll see the same thing.


Matt

Matt Whiting wrote:
That is the same thing people claimed about baseballs, but it turned out
to be a combination of an optical illusion (the mound being higher than
the plate) and people's mind expecting the ball to drop more quickly
than it did and then perceiving this as the ball rising, when it fact it
was simply dropping at a slower rate.

It may not be humanly attainable to make a baseball or golfball "rise",
but it's theoretically possible, right? I think wiffle balls can rise.

Spin is one component that determins the lift produced by the ball.


Spin is one component that is totally ignored when determining the lift
produced by the ball. Calling it lift is based not only on the false
premise that the ball is not spinning but on the intentional ignorance
of the the fact that it is.