as free if its displacements are not restricted by any
other bodies, in opposite case a body is constrained.Examples of free body:
The airplane in the sky is free body.
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Free and constrained bodies. A body treats as free if its displacements are not
Содержание
- 1. Free and constrained bodies. A body treats as free if its displacements are not
- 2. 2. The helicopter is free.
- 3. 3. Bird treats as free body.
- 4. Examples of constrained body.1. The motion of
- 5. The motion of the yellow rectangular plate
- 6. The bodies that restrict the motion of
- 7. Forces classification: applied forces and reactions In
- 8. Some reactions at supports and connections for two-dimensional structure Smooth surfaces
- 9. Weightless flexible, nonstretchable cord orweightless rigid linkSliding joint or roller support
- 10. Pinned joint
- 11. Collar or sliding supportDouble stage sliding supportFixed support, сlamped joint
- 12. Слайд 12
- 13. Some reactions at supports and connections for three-dimensional structureBall-and-socket joint and footstep bearing
- 14. HingeBearing supports
- 15. Fixed support
- 16. Слайд 16
- 17. In the second way forces are subdivided
- 18. Слайд 18
- 19. Concurrent force system If lines of action
- 20. The composition of forces can be accomplished:geometrically,
- 21. Equilibrium conditions for the concurrent force systemTo
- 22. Problems of staticsThere are two general problems
- 23. Moment of a force about a point
- 24. Moment of a force about an axisThe
- 25. Скачать презентанцию
2. The helicopter is free.
Слайды и текст этой презентации
Слайд 1Free and constrained bodies.
A body treats
Слайд 4 Examples of constrained body.
1. The motion of the balloon is
restricted by four cords.
Cord 1
Cord 2
Cord 3
Cord 4
Слайд 5The motion of the yellow rectangular plate ABCD is restricted
by hinges at A and B and is supported by
pined joint link DE.
Слайд 6The bodies that restrict the motion of some body are
called constraints imposed upon the body.
Mechanical effect of a constraint
action is the same as action of a force. Therefore the constraints can be replaced by forces that are called reactions.Axiom of constraint eliminating: any constrained body can be considered free if constraints applied to the body are mentally eliminated and replaced with the corresponding reaction forces.
Слайд 7Forces classification: applied forces and reactions
In mechanics all forces acting
on the body or mechanical system are subdivided into two
classes in two ways.In the first way forces are subdivided into applied (given) and reactive forces. Active (applied) forces are independent from constraints and usually it is supposed that active forces are given in statement of a problem.
Слайд 9Weightless flexible, nonstretchable cord or
weightless rigid link
Sliding joint or roller
support
Слайд 13Some reactions at supports and connections for three-dimensional structure
Ball-and-socket joint
and footstep bearing
Слайд 17In the second way forces are subdivided into external and
internal.
Forces are called external with respect to a given object
(body or mechanical system) if they are produced by particles and other bodies not included into a given object (by external objects). Forces of interaction between particles or parts of the given object are called internal.
Слайд 19Concurrent force system
If lines of action of all forces of
a system intersect at the same point the force system
is called concurrent.Concurrent force system resultant
Concurrent force system is equivalent to single force (resultant). Resultant is equal to the vector sum of the forces of system. Resultant is applied at the point of intersection all forces lines of action.
Слайд 20The composition of forces can be accomplished:
geometrically, constructing a vector
force polygon
analytically, summing projections of all forces
on selected coordinate axes:
Слайд 21Equilibrium conditions for the concurrent force system
To be balanced any
concurrent force system must have zero resultant.
Analytical conditions of concurrent
force system equilibrium In geometrical form it can be formulated as follows: closure of the polygon of forces is a necessary and sufficient condition for the concurrent force system to be in balance.
Слайд 22Problems of statics
There are two general problems of rigid body
statics:
The composition of forces and the reduction of the force
system acting on rigid bodies to the simplest possible form.The determination of conditions for the equilibrium of the force system acting on rigid bodies.
Слайд 24Moment of a force about an axis
The projection of the
moment about the point onto an axis that passes through
the point is called the moment of force about the axis
