On the basis of the law of conservation of angular momentum, discuss why a helicopter must have more than one rotor (or propeller). Discuss one or more ways the second propeller can operate in order to keep the helicopter stable

Thank you. Shouldn't rotational kinetic energy be used, though, for part (b)?

Number 12

A disk slides toward a motionless stick on a frictionless surface (figure below). The disk strikes and adheres to the stick and they rotate together, pivoting around the nail. Angular momentum is conserved for this inelastic collision because the surface is frictionless and the unbalanced external force at the nail exerts no torque. Before M Nail (pivot) (b) What is the kinetic energy (in J) before and after the collision? J K before K J after (b) Consider a situation where the disk has a mass of 52.5 g and an initial velocity of 32.5 m/s when it strikes the stick that is 1.30 m long and 2.20 kg at a distance of 0.100 m from the nail. (a) What is the angular velocity (in rad/s) of the two after the collision? (Enter the magnitude.) X rad/s = After (0) (c) What is the total linear momentum (in kg · m/s) before and after the collision? (Enter the magnitude.) kg. m/s Pbefore kg. m/s Pafter