326 Angular MomentumQ11.9There must be two rotors to balance the torques on the body of the helicopter. If it had only onerotor, the engine would cause the body of the helicopter to swing around rapidly with angularmomentum opposite to the rotor.Q11.10The angular momentum of the particle about the center of rotation is constant. The angularmomentum about any point that does not lie along the axis through the center of rotation andperpendicular to the plane of motion of the particle is not constant in time.Q11.11The long pole has a large moment of inertia about an axis along the rope. An unbalanced torque willthen produce only a small angular acceleration of the performer-pole system, to extend the timeavailable for getting back in balance. To keep the center of mass above the rope, the performer canshift the pole left or right, instead of having to bend his body around. The pole sags down at theends to lower the system center of gravity.
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