BE 1707 Dynamics Study Question
ID:1916379
Teodor Karamichev
(a) Explain the difference between a “particle” and a “rigid body” making reference to
the difference in their respective degrees of freedom.
Particle
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Dimension are very small (infinitely small volume)
Particles does not have internal structure(elementary)
No moments act on a particle, because it is concentrated in one point.
Object of negligible dimensions as far as the distance travelled or its motion is
concerned
Rotation is not of concern and in 3-D space we have translation {x, y, z}, which means
that particles have 3 Degrees of Freedom (Dof)
Rigid body
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It is composed of particles itself (It is large)
Moments are relevant.
Rigid Bodies does have internal structure or composite particles.
A rigid body is a body whose every constituent elements maintains the same relative
distance even when subjected under force.(deformation is zero and it is completely
stationary)
Object of non-negligible dimensions, however the its change in shape is negligible or
ignored
Rotation is also considered, hence in 3-D space we have {x, y, z} &
{ψ, Ф, θ}, which means that rigid bodies have 6 Degrees of Freedom(Dof)
(b) Explain what a reference frame is and why it is used in solving dynamical systems
Reference frame, is a system of graduated lines symbolically attached to a body that
serve to describe the position of points relative to the body. It is also known as frame
of reference. The reference frames used in dynamics are known as coordinate
systems with axes (lines) emanating from a point known as the origin.
We assume that the earth is at rest, for example, and analyse the motion of any
moving object. Under any other condition analysing will become so complex and
there would be a lot of variables and that is why we use frame of reference in solving
dynamical equations.