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1. Stresses that occur in the system at impact, exceeding the
limit of proportionality is not material, that you can
always use Hooke's law.
2. Beat is considered to be perfectly inelastic (no bouncing).
That falling mass after the impact as sticks to the body
that suffers blow, then they continue to move along.
3. The local deformation arising in contact bodies is not
considered.
4. We consider cases where the weight of an elastic body
that suffers blow-up compared to the weight that has an
impact. Therefore, we consider massless elastic system.
At the same time neglect the phenomenon of wave
propagation strain.
5. We believe that the kinetic energy of a falling body is
completely transformed into potential energy of elastic
deformation of the body that accepts a challenge.
6. Law distribution of stresses and strains on the volume of
the body that suffers stroke, remains the same as in the
static action forces.
Based on these assumptions determine the displacement
and stress arising in the bars at impact.
Note that, in the technical theory of shock we can if
necessary to take into account the influence of the mass elastic
system. This increases the accuracy of the calculations.

7.2.2 Longitudinal impact

Let the rod length l with a height h of free fall load (fig.
7.3 a). The absolute elongation of the rod, which is caused by the
dynamic longitudinal force N is denoted l . Since the velocity
д д
of the incident shock load at the end is zero, the change in kinetic
energy equal to the work force P , i.e.
A P h   l д  , (7.9)
and potential energy of elastic deformation of the rod
1
l
U  N  . (7.10)
д
д
2

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