Helmet Fire, I guess I don't need to introduce any more examples, but I'd like to comment on your experiment. You stated it this way...
Get a large easy to see object with some weight, such as a full soft drink can or water bottle. Go out side with a friend. Face a very obvious marker, such as a distant white building or even use your friend. Hold the object out at arms length from your body, DIRECTLY TO YOUR FRONT, so that as you turn your body, your arm stays straight out in front. Spin around. When you and your hand are exactly facing your marker, open your hand.
OK, instead of performing this experiment, let's just diagram it. We'll assume that the direction of rotation is counter-clockwise when looking from above. The diagram will consist of 3 points, 1 circle, and 3 lines. The explanation that follows may sound a little complicated, but actually it's very easy to free hand draw the diagram.
First, on a sheet of paper (oriented landscape style in front of you), draw a point (point A) in the horizontal center about 2/3 down from the top. This represents where your feet will be when you spin. Draw a circle around point "A" with a radius that represents a scale of the distance to the hand on your outstreched arm. Lets say the radius is 2 feet for simplicity. Next, draw another point (point B) in the horizontal center, towards the top of the page directly above point "A". This point will represent your friend at a scale distance from you of say 10 feet.
Next, draw a line (line A) that is vertical on the page, starting at point "A" and passing through point "B". The point (point C) where this line (line A) intersects the circle, is the location of the release point for the soft drink (or bottle of water), directly in front of your friend. Next, draw a line (line B) that is horizontal on the page and passing through point "A". This line then, should pass through the center of the circle, and also be perpendicular to line "A". Finally, draw a line (line C) that is horizontal on the page and begins at point "C" (on the circle) and draw it towards the left edge of the page. This line should be parallel to line "B".
Now you've finished the diagram.
You said in a response to Lu...
You are right according to my results - the object does not fly outwards at all, it flys tangentially.
You are partly right and partly wrong. If when you said "the object does not fly outward at all", you meant that the object does NOT follow line "A" directly towards your friend, then yes you are correct. No force exists in this experiment to cause the soft drink to turn 90 degrees to the right, immediately upon release, in order for it to impact your unsuspecting friend.
You (and Lu) are also correct when you say that the soft drink will fly "tangentially". However, you are wrong if when you said "the object does not fly outwards at all", you meant that the object does not display ANY motion away from the center of rotation. It does in fact display this motion, because it's new path of motion, immediately after release, will be along line "C". Remember that this line is parallel to line "B", the line that runs directly through the center of the circle (of rotation). While there is "tangentail" motion relative to the center of rotation, the motion is still "largely" away from that center. The object's resistance to "directional" acceleration (caused by its own inertia) is still trying to move the object away from the center of rotation, even if that motion is along line "C" and is partly "tangential".
While the object is in rotation, point "C" (the release point) will keep moving around the cicle until a release actually occurs. The object's resistance to "directional" acceleration will cause it to continually try to follow this path (represented by line "C"), and the force this creates against the "centripetal" pull (or force) is very real, and is in fact the "centrifugal" force.
So in the end there is still enough of this motion away from the hub (or center) to make devices like the centrifugal clutch work.
(edited for spelling and typos)
(edited again to reformat the text into normal paragraphs)
Last edited by Flight Safety; 1st April 2002 at 02:44.