Direction of rotation.???

[P Timmy]

The link below shows a slow motion video of a rotating hammer (beginning at 2:01)... in which direction do you see the hammer rotating.???

http://www.youtube.com/watch?v=Jpbgg2TRCuw


EDIT:::
I want to know which direction you see the hammer rotate in the slow motion part of the video I indicated... not which direction you think it should be rotating... and please vote in the Poll.!!!

[Hornblower]

As seen from the side it is difficult to see which way it was turning. I would expect it to be counterclockwise as seen from above, which is the same direction she was turning when throwing it.

[P Timmy]

As seen from the side it is difficult to see which way it was turning.

I can clearly see it rotating CW.!!!

[Solfe]

I suspect it is moving counter clock wise from hand positions. The athlete is spinning counter clockwise, her hands must move in a counter clockwise fashion while passing in front of her body/face and "snap" in the opposite (CW) direction before starting the next revolution. The clockwise motion is required to keep the hammer stable. If it did not it would have to rotate in her hands.

[P Timmy]

The link below shows a slow motion video of a rotating hammer (beginning at 2:01)... in which direction do you see the hammer rotating.???

http://www.youtube.com/watch?v=Jpbgg2TRCuw

As seen from the side it is difficult to see which way it was turning.

I suspect it is moving counter clock wise from hand positions.

Hi Solfe... I'd like to know which direction you see the hammer rotating in the slow motion part of the video... not which direction you think the hammer should be rotating... and Hornblower... does the hammer appear to be rotating to you.???

To all who view the video... please answer the poll.!!!

[Solfe]

There are way too many artifacts in the video to be 100%, but I get the impression the head of the hammer is turning counter clockwise while the chain and handle are moving in the opposite direction.

My prior post is based on personal experience with screwing up with weapons, things like nunchucks (Wii or otherwise) will do the exact opposite thing you expect if you upset them. My personal favorite is when the chain or stick strikes your thumb knuckle (which doesn't hurt at all) and causes the other end to turn and strike you some place between the knees and forehead.

[P Timmy]

My prior post is based on personal experience with screwing up with weapons, things like nunchucks...

My personal favorite is when the chain or stick strikes your thumb knuckle (which doesn't hurt at all) and causes the other end to turn and strike you some place between the knees and forehead.

Yes it surly isn't as painful as one might expect or people wouldn't do it... but still... I think beginners should start out nice and easy like the guy in the link below.!!!

http://www.youtube.com/watch?v=A3NSb434e-4

[Hornblower]

Hi Solfe... I'd like to know which direction you see the hammer rotating in the slow motion part of the video... not which direction you think the hammer should be rotating... and Hornblower... does the hammer appear to be rotating to you.???

To all who view the video... please answer the poll.!!!

It is obvious that the chain is revolving around the ball. I cannot tell which way by looking at this video, because there is not enough detail visible to indicate which half of the cycle has the chain between us and the ball. Nothing ever transits the ball visibly, and there are no visible mark on the ball.

[P Timmy]

It is obvious that the chain is revolving around the ball. I cannot tell which way by looking at this video, because there is not enough detail visible to indicate which half of the cycle has the chain between us and the ball. Nothing ever transits the ball visibly, and there are no visible mark on the ball.

Nicely explained :-)

And much like the Spinning Dancer Illusion... some people will see the hammer appear to rotate CW and some will see it appear to rotate CCW because of the reasons you explained above... and also... the hammer can be seen to oscillate back and fourth without making a complete rotation.!!!

This issue came up years ago when a guy (kdine) questioned why the hammer was rotating CW during its flight down the field when the hammer thrower was clearly rotating CCW when they released the hammer.!!!

[speedfreek]

At 2:06 the handle is clearly moving left and passing behind the hammer. Anticlockwise it is.

Note: I jumped straight to 2:01 to watch the hammer, before going back to see what direction the thrower was rotating. I was correct!

[P Timmy]

At 2:06 the handle is clearly moving left and passing behind the hammer. Anticlockwise it is.

Note: I jumped straight to 2:01 to watch the hammer, before going back to see what direction the thrower was rotating. I was correct!

Yes the hammer is actually rotating CCW... but with the Spinning Dancer illusion... most people can see it rotate CW or CCW... can you also see the hammer rotate CW.???

[Jeff Root]

I watched the slow-motion part about 20 - 25 times.

While the hammer is in front of the audience, it is
rotating clockwise relative to the camera.

The chain *seems* to go on the far side of the ball just
before the hammer passes in front of the running track
and grass, becoming hard to see. So up to that point,
it is rotating clockwise relative to the camera, and
counter-clockwise as viewed from above. As a result,
I did not vote in the poll. No choice for "Both".

-- Jeff, in Minneapolis

[P Timmy]

I watched the slow-motion part about 20 - 25 times.

While the hammer is in front of the audience, it is
rotating clockwise relative to the camera.

The chain *seems* to go on the far side of the ball just
before the hammer passes in front of the running track
and grass, becoming hard to see. So up to that point,
it is rotating clockwise relative to the camera, and
counter-clockwise as viewed from above. As a result,
I did not vote in the poll. No choice for "Both".

The poll didn't draw as much interest as I had hoped... I figured the people who saw both directions of rotation would answer "other".!!!

[wiggy]

I assume you mean if viewed from above. Clockwise.
I didn't watch the rest of the video to be swayed by the video of her winding up.
Visually, with no prior conceptions or ideals on one single watch, it looked clockwise.

[swampyankee]

To me, in all of them, it looks, from the rear, like the throwers' right arms are moving forward when they are facing away from the camera. That means they're turning counterclockwise (observer looking down), so the hammer will also be turning counterclockwise when seen from above.

I wonder if these throwers were all right-handed, and, if so, whether left-handed throwers would spin clockwise.

[HenrikOlsen]

they're and they're

[P Timmy]

I assume you mean if viewed from above. Clockwise.
I didn't watch the rest of the video to be swayed by the video of her winding up.
Visually, with no prior conceptions or ideals on one single watch, it looked clockwise.

The view I'm going by is the exact view shown in the video... and at first... the direction of rotation in the slow motion part of the video looked CW to me... but since it was pointed out that the direction of rotation can appear either way... I can now see it rotate CW or CCW... even though I know it's actually rotating CCW.

To me, in all of them, it looks, from the rear, like the throwers' right arms are moving forward when their facing away from the camera. That means their turning counterclockwise (observer looking down), so the hammer will also be turning counterclockwise when seen from above.

I wonder if these throwers were all right-handed, and, if so, whether left-handed throwers would spin clockwise.

Yes it's actually rotating CCW even in the slow motion part of the video--it was just a fun puzzler as to why some saw CW rotation and some saw CCW rotation.

Some hammer throwers spin CW.

[Jeff Root]

Judging from just the close-up slow-motion, whether we see it
from "above" or "below" is unclear-- perhaps impossible to judge,
thus we can't tell for sure whether it is rotating clockwise or
counterclockwise as seen from above (or below!). However,
it is unambiguously rotating clockwise as seen from the camera's
viewpoint. So anyone who doesn't know the full story-- and doesn't
claim to be able to judge from the visual cues alone whether we
are seeing it from "above" or "below"-- should say that it appears
to be rotating clockwise. But they should also specify that that
is relative to the camera's position.

-- Jeff, in Minneapolis

[P Timmy]

Yes the hammer is actually rotating CCW... but with the Spinning Dancer illusion... most people can see it rotate CW or CCW... can you also see the hammer rotate CW.???

...it is unambiguously rotating clockwise as seen from the camera's
viewpoint. So anyone who doesn't know the full story-- and doesn't
claim to be able to judge from the visual cues alone whether we
are seeing it from "above" or "below"-- should say that it appears
to be rotating clockwise. But they should also specify that that
is relative to the camera's position.

In the spinning dancer illusion (above)... can you unambiguously see the lady rotate CW or CCW?

[Jeff Root]

I spent quite a long time looking at that. I finally got her to
go clockwise as imagined from above, and eventually could
keep her going clockwise for maybe half a minute, or make
her switch directions almost at will. Even after doing it many
times it looks impossible that it could change directions. But
then it happens!

-- Jeff, in Minneapolis

.

[swampyankee]

they're and they're

Fixed, and thank you. Need to reboot my grammar processor.

[Perikles]

In the spinning dancer illusion (above)... can you unambiguously see the lady rotate CW or CCW?

I can select which way I want her to rotate, and get her to change direction. I started a thread on this some time ago.

[profloater]

agreed; this is an old illusion and with a little practice you can make the apparent rotation switch just like the transparent table with four legs illusion can switch to seeing it from above or below. Once you have mastered it, the switch gets easier so I guess it is a brain function that can be trained rather like getting used to wearing bi-focals. A similar effect happens with those pictures that are pixelated and if you deliberately defocus you see an object in apparent 3D, it can take a long time to see it at first and then it is obvious. The brain is a remarkable vision processor!

[P Timmy]

Originally Posted by P Timmy
Yes the hammer is actually rotating CCW... but with the Spinning Dancer illusion... most people can see it rotate CW or CCW... can you also see the hammer rotate CW.???

Originally Posted by Jeff Root
...it is unambiguously rotating clockwise as seen from the camera's
viewpoint.

In the spinning dancer illusion (above)... can you unambiguously see the lady rotate CW or CCW?

Even after doing it many times it looks impossible that it could change directions. But then it happens!

Do you agree that from the camera angle in the slow motion part of the hammer throw video I specified... that the hammer can be seen to rotate CW or CCW... just like the dancing lady illusion?

I can select which way I want her to rotate, and get her to change direction.

agreed; this is an old illusion and with a little practice you can make the apparent rotation switch

Can you two also make the hammer switch its direction of rotation (in the slow motion part of the video I specified)?

[Jeff Root]

Do you agree that from the camera angle in the slow motion
part of the hammer throw video I specified... that the hammer
can be seen to rotate CW or CCW... just like the dancing lady
illusion?

Of course. I think everyone understood that from the start.
At least I did. If I hadn't understood it, I would have thought
your question was crazy. There is obviously not enough detail
in the slow-motion shot to make the direction of rotation relative
to the vertical (which is the tacit standard) obvious.

On the other hand, not much detail is needed to make the
direction of rotation relative to the camera obvious, and that
detail is present.

In the slow-motion of the hammer, we have information which
tells us fairly exactly where the vertical is, but almost none
which tells us when the chain is closer to the camera than the
ball. In the dancer animation, we have only spurious cues as
to when parts of the dancer's body are closer to the camera.
Those cues are false -- only imagined by the viewer. There is
no perspective or any other other real cues that might possibly
be found in the video. The direction of vertical in the animation
is ambiguous in the radial direction from the camera.

-- Jeff, in Minneapolis

[P Timmy]

Do you agree that from the camera angle in the slow motion part of the hammer throw video I specified... that the hammer can be seen to rotate CW or CCW... just like the dancing lady illusion?

Of course.

That wasn't clear since you only mentioned "clockwise" in your post below.

Originally Posted by Jeff Root
...it is unambiguously rotating clockwise as seen from the camera's
viewpoint. So anyone who doesn't know the full story-- and doesn't
claim to be able to judge from the visual cues alone whether we
are seeing it from "above" or "below"-- should say that it appears
to be rotating clockwise. But they should also specify that that
is relative to the camera's position.