If angular momentum were not conserved, one might find an isolated body developing a spontaneous rotation with respect to the distant stars or, if rotating like the Earth, changing its rotational speed without any external cause.
Any change in the angular momentum of the body is given by the torque equation, An example of a body that undergoes both translational and rotational motion is the Earth, which rotates about an axis through its centre once per day while executing an orbit around the Sun once per year.
Conversely, an observer on the ground sees and measures only the relative motion of the atmosphere, because he is also rotating and cannot see directly the rotational motion applied by Earth.
The slowing of the planet's initial high rotation rate by tidal forces (see above Orbital and rotational effects) would have produced compression in Mercury's equatorial latitudes.
In the gas phase, where they are widely separated relative to their size, molecules can undergo free rotation and as a result possess quantized amounts of rotational energy.
Another way of putting the same point is to say that, in Newtonian mechanics and special relativity, rotation is "absolute" because the transformations between inertial frames (Galilean or Lorentzian) preserve rotational states.
Andaman Discoveries runs one of the country's best-organised programmes, born out of the North Andaman Tsunami Relief fund, which places visitors in homes on a rotational basis to spread the benefits around villages along the Andaman coast.
All that was needed to make a mechanical energy-storage system was a good enough rotational seal, so the flywheel could spin freely inside a vacuum chamber with no air resistance.By all accounts, the sealing problem has now been licked as well.
The single set of rotors on a standard helicopter produces a rotational force, or torque.
Traditional helmets are good at protecting against linear acceleration, but offer limited protection against rotational forces.
So when a head hits a surface, the scalp absorbs some of the rotational part of the impact by moving across the skull.
