can anybody explain me right handed screw rule
It exists for many systems. For what did you see it?
Let the fingers of your right hand curl naturally. When you turn a screw the direction your fingers point the screw will move the direction your thumb is pointing.
This is the only way I can be sure that I am turning a screw in the appropriate direction.
righty tighty lefty loosey
but remember that you are going "right" from the top of the circle. From the bottom you'd be going left
If you're talking rotational motion, if you point your thumb and curl your fingers, your fingers are curling in the positive direction for rotational motion. That means that if you're viewing from outside the system (your thumb is pointed at your face) positive direction is counter clockwise. If you're viewing from the system (base of your hand towards your face) positive direction is clockwise. You can't use clockwise or counter-clockwise without a frame of reference. The right hand screw rule works, regardless of the frame of reference.
What the force vector said to the torque vector :
Consider three vectors, A, B and C which have coincident initial points and are not coplanar - these vectors form a "right handed system" if a right threaded screw rotated through some angle less than Pi from A to B advances in the direction of C.
The normal 3D coordinate system we are all familiar with (x,y, and z axes) is a "right handed system."
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