# rotating

18. ### Torque on barbell when angular momentum is not constant

1. Homework Statement Consider a barbell with two equal masses m that rotates around a vertical axis z not passing through its center with angular velocity \vec{\omega}. The barbell is forced to stay in this position by an appropriate support. Identify the forces exerting torques on the system...
19. ### System of ODEs in a rotating coord. system

1. Homework Statement imgur link: http://i.imgur.com/pb14Q4Q.png 2. Homework Equations 3. The Attempt at a Solution The thing I don't understand is where the first two terms of each 2nd order ODE came about. I understand that they are there because the coordinate system is rotating...
20. ### Mathematical modeling of the deflection of a rod

A rod is radially mounted on a motor shaft and provided with a flat end plate. By turning movement, the end plate will touch a pointed object, and the angle turned is measured.By the torque of the motor during acceleration and deceleration, a vibration and deflection happens on the rod. The...
21. ### Why is kinetic energy due to a planet's rotation treated as negative?

1. Homework Statement I am trying to answer the following question: Among the animals that appear in the zoo of the Universe there are black holes and neutron stars. The mass of each of these is often the order of the mass of the Sun. The radius of a neutron star is about 10 km and a certain...
22. ### Kinetic energy of a rotating and translating body?

1. Homework Statement Not a homework or coursework question, but given the simplicity of the problem I feel that this is an appropriate subforum. Consider a person spinning a rock on a string above their head at a constant angular velocity, walking away from the observer at a constant linear...
23. ### Confusion with the centrifugal foce and potential energy

When we release a suspended object, we recover the potential energy due to gravity as the object travels back through the height raised. When we release an extended spring, we recover the potential energy as the object travels back through the distance stretched. But when we release a rotating...