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7 DYNAMIC PROBLEMS

7.1 Consideration of inertial forces at constant
acceleration

Consider a few examples of the simplest kinetic static
method for determining the stresses in the elements of design,
moving with constant acceleration.
Stresses in rope hoist. Let the load Q is raised with a rope
to which it is attached, with a constant acceleration a (fig.7.1 a).
Area cross section rope - F , density material -  . Determine the
normal stress  in any cross section pulling away x from its
lower end, taking into account, in addition to cargo rope Q own
weight and inertial forces.

а

b)
Figure 7.1

Effective force P , that occurs at the accelerated motion of
the load and rope length x , has a direction opposite to the
direction of acceleration, and is equal to:
 Q  a
P  ma    F x a  Q  F gx  , (7.1)


 g  g

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