Assertion: helicopter's rotor | /r/CapableOf | spin in opposite directions
Facets:
Source sentences:
text: Some helicopters have two horizontal rotors which spin in opposite directions, allowing the helicopter to lift heavier objects.
text: Nelson also realized that the rotors had to spin in opposite directions; otherwise a peculiar force of physics which engineers call "torque" would turn his car in one direction while the fans revolved in another.
text: The rotors were arranged one above the other and spun in opposite directions, principles still used in modern twin-rotor designs.
text: Since the two rotors are spinning in opposite directions, the total angular momentum is zero and there is no need for torque from an extra tail rotor.