Page 84 - 4560

instant braking. For example, when braking fast-rotating shafts,
bearing flywheels (fig. 7.6).
The kinetic energy of a
rotating flywheel in motion

1
2
T  J ,
2
2
where J  0,5mR – polar
moment of inertia of the mass
of the flywheel rotating with
angular velocity  .
Figure 7.6 The potential energy of
deformation of the torsion

shaft
1  2 l
U  M   д ,
д
2 2GJ

where   M l GJ – angle of twist of the shaft.
д 
Then the energy conservation law takes the form
2
1 2 M l
д
J  ,
2 2GJ

where we define the torque acting on the shaft cross section
GJ J
M    . (7.23)
д
l
Then by the known formulas, we can determine the shear stress
and angles of twist of the shaft sections.

7.2.5 Account the weight of the rod, which suffers blow

If the net weight of the rod Q and falling weight load P
(fig. 7.3) - the value of the same order, the inertia weight rod
should be considered, as this can significantly affect the results of
the calculations.
If the rod is massless, we have

84