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regardless of external forces exerted on it. In classical mechanics a
rigid body is usually considered as a continuous mass distribution
In mechanics, degrees of freedom (DOF) is the number of
parameters that define the configuration of a mechanical system. The
degrees of freedom of a body is the number of independent parameters
that define the displacement and deformation of the body. This is a
fundamental concept relating to the systems of moving bodies in
mechanical engineering, aeronautical engineering, robotics, and
structural engineering.
The position of a single car moving along a track has one degree of
freedom, because the position of the car is defined by the distance along
the track. A train of rigid cars connected by hinges to an engine still has
only one degree of freedom because the positions of the cars behind the
engine are constrained by the shape of the track.
An automobile can be considered to be a rigid body travelling on a
plane (a flat, two-dimensional space). This body has three independent
degrees of freedom consisting of two components of translation and one
angle of rotation. Skidding or drifting is a good example of an
automobile's three independent degrees of freedom.
The position of a rigid body in space is defined by three
components of translation and three components of rotation, which
means that it has six degrees
The motion of absolutely rigid body includes the motion of the
center of mass and rotations around axis that pass through the center of
mass. Translation motion of absolutely rigid body is such motion when
any line closely connected with the body moves parallel to the initial
position
All points of an absolutely rigid body at the same time pass the
same distances, hence, the velocities v and accelerations a for all points
of the absolutely rigid body are equal. Therefore consideration of
translation motion of the absolutely rigid body reduces to the study of
motion of its arbitrary point (for example, the center of mass).
Consider a rigid body of triangle form as shown in fig.1.11. First
position a illustrates translation motion when this body moves parallel
in three direction , three axis OX, OY, OZ and therefore three are three
degrees of freedom on translation motion
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