Rigid body Definition and 356 Threads

In physics, a rigid body (also known as a rigid object ) is a solid body in which deformation is zero or so small it can be neglected. The distance between any two given points on a rigid body remains constant in time regardless of external forces or moments exerted on it. A rigid body is usually considered as a continuous distribution of mass.
In the study of special relativity, a perfectly rigid body does not exist; and objects can only be assumed to be rigid if they are not moving near the speed of light. In quantum mechanics, a rigid body is usually thought of as a collection of point masses. For instance, molecules (consisting of the point masses: electrons and nuclei) are often seen as rigid bodies (see classification of molecules as rigid rotors).

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  1. K

    Angular momentum of a rigid body

    The angular momentum of a rigid body is often calculated into different coordinate systems. One is an inertial system and the other is a body system moving with the rigid body. Now, in the body system the rigid body is at rest and has no movement at all. How is it that it can still have a...
  2. A

    Molecular Dynamics vs Rigid Body Dynamics

    How different/similar is molecular dynamics from rigid body dynamics? Could I use RBD software such as ODE to simulate MD? What assumptions/modifications would I need to make for this to work (e.g. treat atoms as rigid spheres connected through some special type of joints)?
  3. D

    Calculate the torque on a rigid body

    Can someone please tell me if it is possible to calculate the torque on a rigid body without specifying the origin?
  4. E

    Exploring Rigid Body Motion: Understanding the Need for 6 Coordinates

    Any good links to lecture notes or anyone can explain the underlying concepts here? Are we just dealing with a summation of points constituting a single object? I am sorry if this question is too general or broad. Maybe a more specific question is why there are 6 coordinates needed to describe...
  5. A

    Effective Forces on a Rigid Body

    A question about Dynamics and drawing FBDs. In our book, we have an equation that says: \Sigma M_O = \Sigma M_{O(effective)} Most of the time, this basically translates into: \Sigma M_O = \overline{I}\alpha. The left-hand side basically represents the sum of the moments of all the...
  6. denian

    Effect of Material on Angular Momentum of a Pivoted Disc

    a thin metallic disc pivoted at its centre, and there is a resultant torque act on it. moment of inertia about its centre is 1.50 kgm2 if the metallic disc is replaced by another identical wooden disc, state qualitatively the effect on the angular momentum of wood. my tutor told me that...
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