The main rotors on many helicopters turn counter clock-wise (eg Bell).?
966020
Probably due to helicopter manufacturer patented design thing. It doesn't matter as to what direction the rotor should turn for so long as it goes along the direction of the blades.
246928
razor may be thinking of a Darrieus machine which does have a vertical spin axis. But a downwind turbine has a normal fan-type rotor whose blades are on the lee side of the support mast (ref.). If built without excessive nacelle area on the windward side, this just naturally yaws in the proper direction due to the wind force on the rotor driving it leeward. Another advantage is that the rotor can be more flexible because collision with the mast is normally not possible. However as the ref. points out, there are also disadvantages to this design, including cyclic blade loads due to the support's wind shadow.
595431
For the most part, yes. Low pressure systems in the Northern Hemisphere spin counterclockwise and Highs spin clockwise. The reverse is true in the Southern Hemisphere.
852362
I would like to say thanks to the Coriolis effect, toilets flush clockwise in the northern hemisphere and counterclockwise in the southern.  But it is not true.\nThe twisting effect of the Coriolis force is real and does influence certain large things like the movement of air masses, but the effect is so small that it plays no role in determining the direction in which water rotates as it exits from a draining sink or toilet. The Coriolis effect produces a measurable effect over huge distances and long periods of time, neither of which applies to your bathroom. Toilets and sinks drain in the directions they do because of the way water is directed into them or pulled from them. If water enters in a swirling motion (as it does when a toilet is flushed, for example), the water will exit in that same swirling pattern; as well, most basins have irregular surfaces and are not perfectly level, factors which influence the direction in which water spirals down their drains. The configuration of taps and drains is responsible for the direction of spin given to water draining from sinks and bathtubs to a degree that overwhelms the slight influence of the Coriolis force.
391947
That depends, how much time was in between each ring and how systematic are the rings (and what guarantee is there the rings will continue to be at the same intervals)?  \n\nThat is, if the bell rings one time in the first five second and twice in the last three, it could ring three more times in the next four seconds or take six hours [or any amount of time] to ring another three.  Maybe it won't ring again!  \n\n(And I am assuming the three rings you mention are included in the six you want in the final answer.)
804036
stationary : stator\nrotating: rotor
53243
I have to assume that you're familiar with general aerodynamics. If not, there's really not enough space to answer your question here.\n\nThe biggest physics differences between a helicopter and an airplane are torque, translational lift, and retreating blade stall.\n\nA helicopter's fuselage will tend to turn opposite the direction of the rotor, particularly at a hover or a slow speed. (Some streamlining occurs in flight.) The "tail rotor" is actually called an "anti-torque rotor" because its installation is designed to counteract the main rotor's torque. (Notice that twin rotor helicopters don't have anti-torque rotors because the main rotors rotate in opposite directions and counteract each other's torque.)\n\nNext is effective translational lift. At a hover and at slow speeds, generally below 30 KIAS, a helicopter is flying in its own rotor wash. A lot more lift and constant control inputs are required to maintain steady flight. Lift in a helicopter is created by the rotating blades and is increased (or decreased) by raising the collective (a “joystick by the pilot’s left leg) which increases (or decreases) the rotor’s angle of attack. Note: During all of this, the rotor maintains a constant R.P.M….it does not spin faster when climbing and slow down when descending.\n\nAlso, some of this lift is used for thrust to move the helicopter forward, or sideways, or backward. This is why you see a helicopter nose down when it’s taking off. The rotor is the “wing and the propeller” at the same time.\n\nFinally, retreating blade stall limits the speed of a helicopter. Sitting on the ground and in a still wind at operating R.P.M. the wind is blowing over the blades at a steady speed. (Of course the blade root’s speed is much lower than the blade’s tip because it has less far to travel.) But in forward flight at, say 100 KIAS, the advancing blade has an extra 100 knots relative wind added to its speed. The retreating blade, going opposite to the relative wind is LOSING 100 knots relative wind. The faster you go, the more the retreating blade loses lift and eventually stalls; that is loses lift completely and the helicopter will roll over.\n\nThis is about all I can tell you in a short time, but it’s all very interesting and surprisingly inefficient. I’ve attached some links that will go into more detail. Hope this helps!
973527
That's an urban legend.  Windmills are generally set up to rotate in a way that makes the most out of the prevailing local wind.  If you look at windmills you will find that they do not all rotate the same way.
23313
The UH-1N is a twin-engine helicopter\nhttp://www.hqmc.usmc.mil/factfile.nsf/0/0fcbc129ac3dd43c8525626e0049668b?OpenDocument
177393
Blank Pictures of alarm clocks.\n\nhttp://www.blackdog.net/games/clock/worksheets/fourclocks.gif
305100
That would be "counter-clockwise" not "anti-clockwise". Motor sports in Australia are generally run with the drivers turning right on ovals, so that's probably what you saw, unless you are referring to a road course.
462355
http://en.wikipedia.org/wiki/Digital_clock
870916
There is a weight mounted off-balance on a shaft so that it hangs down. It has a one-way ratchet connected to a reduction gear so that motion in one direction winds the spring. In the other direction the shaft just turns freely.\n\nAs you move about, walking, running, gesturing, whatever, your wrist moves back and forth. As your wrist changes position the weight causes the shaft to turn and the ratchet captures the motion to wind the main spring.
1030248
Southern Bell with british backside
431766
Most of the time, yes.  For instance, almost all tornadoes in the Northern Hemisphere are counterclockwise.  However, because of their small size, there is a small fudge factor that can allow the rare anticyclonic tornado, and these have been recorded.
1045896
Bell H-13, HTL-4 helicopters
25693
Down. Clockwise or anti-clockwise rotation is very much dependent on the first impulse when you open the drain, with coriolis force a distant second.