Problem 6. (18 pts) An instructor stands at the 5.0 kg dumbbell in each hand. He

Question

Problem 6. (18 pts) An instructor stands at the 5.0 kg dumbbell in each hand. He is set rotating about the vertical axis by a force applied tangentilly to the rotation to produce a torque of 2 N m. After 2 rotations the force is removed and the instructor spins with arms still outstretched. Find the final angular speed of the instructor once she pulls both dumbells inward into her stomach knowing that, in the process, the moment of inertia of the instructor changes from 3.0 kg m2 to 2.2 kg m2 center of a frictionless turntable with arms outstretched and the Problem 7.Conceptual (7 pts) The angular momentum of a system remains constant A) when the total kinetic energy is constant. B) when no net external force acts on the system. C) when the linear momentum and the energy are constant. D) when no torque acts on the system E) all the time since it is a conserved quantity Problem 8. (18 pts) A box of mass M 50 kg hangs from by a rope from a boom with dimensions a 1.8 m and b 2.5 m. The boom consists of a hinged beam and a horizontal aluminum cable (Young's Modulus = 7x1010 Pa) with a cross section of 1x10-2m2. The uniform beam has a mass of 85 kg. Find by how much the cable elongates under the weight of the box. uminum cable Problem 9. Conceptual. (5 pts) Tensile stress is A) the strain per unit length. B) the same as force. C) the ratio of the change in length to the original length. D) the applied force per cross-sectional area. E) the ratio of elastic modulus to strain. Problem 10. (10 pts) what is the torque about the origin on a particle located at r force F-5 Ni-2Nj+3 N k acts on the particle? 3 mit 4 m ?-2 mk ifa

Explanation / Answer

(7) The angular momentum of a system remains constant when no torque acts on the system.

(9) Tensile stress is the applied force per cross-sectional area.

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