statics
Principle of transmissibility of a force
states that the external effect of a force on a body is the same for all points of application along its line of action it is independent of the point of application
couple
we define a _____ as made up of two equal parallel oppositely directed forces
Conditions of equilibrium for moments
we express the conditions of equilibrium in terms of moments summations instead of x and y summations
In Dynamics
you considered a motion of rigid body's caused by the forces acting upon them
vector quantities
Quantities which possess magnitude and direction are defined as
scalar quantities
Quantities which possess magnitude only and can be added arithmetically are defined as
couple
The special case in which the result and a zero magnitude but does have a moment is said to consist of a
equilibrium
The subject matter of statics as its name implies deals essentially with the action of forces and bodies which are at rest such bodies are said to be in _____ term used to designate the condition where the resultant of a system of forces is zero
Statics and Dynamics
The subjects divides naturally into two parts
external effect of a forces
This concept of the moment of a force can be used to demonstrate the principle of transmissibility namely ______ the independent of where it is applied along its line of action
A force system
is any arrangement where two or more forces act on a body or on a group of related bodies.
Rigid body
is defined as a definite amount of matter the parts of which are fixed in position relative to each other
A free vector
is defined as one which does not show the point of application of the factor as distinguished from a localized vector which does
The advantage of expressing equilibrium in terms of moment summations
is that any particular force can be eliminated by taking moments about the center of its line of action this method is specially useful the force to be eliminated is specified interaction by its slope
The moment of a force about an axis or line
is the measure of its ability to produce turning our twisting about the axis
The internal effect of a force
is to produce stress and deformation in the body on which the force acts
In equilibrium of non-concurrent for system
it was demonstrated that the resultant of a non-concurrent for system could be determined from the components summation of x summation of y and summation of m
horizontal and vertical axis. using rotated access .using force triangle
m1, m2 .m3
A set of forces in equilibrium
may be added to any system of forces without changing the effect of the original system
Force
may be defined as that which changes are tends to change the state of motion of a body this definition applies to the external effect of a force
Force
may be defined as that which changes or tends to change the state of emotion Of a body
Engineering mechanics
may be defined as the science which considers the effects of forces and rigid bodies
The coplanar system
obviously simplier than non-coplanar systems since all the action lines of the force lie in the same plane
External effect
of forces are considered in engineering mechanics while internal effects are considered in strength of materials
Two forces are in equilibrium
only when equal in magnitude opposite and direction and collinear in action
the parallelogram law
resultant of two forces is the diagonal of the parallelogram formed in the vectors of these forces
A parallel force system
s1 on which the action lines of all the forces are parallel the resultant of such system is determined when it is known in magnitude direction and position
In static
so you can see there the effects and distribution of forces and rigid bodys which are And remain at rest
rigid bodies
. In many cases this deformation is negligible compared to the size of the body and the body may be assumed ______ made of steel or cast iron for example are of this type
equilibrium
A body is said to be in ____ when the force system acting upon it has a zero resultant
a free body diagram
A sketch of the isolated body which shows only the forces acting upon the body is defined as
concurrent
Forces whose lines of actions pass through a common point are called
non-concurrent for system
Forces in which neither are parallel nor intersect in a common point are known as
parallel force systems
Forces whose lines have action are parallel are called
the fundamental anxioms of mechanics
The principles of mechanics are postulated upon several more or less self evident facts which cannot be proved mathematically but can only be demonstrated to be true we shall call these facts
determining the equations that produce a zero resultant
The conditions of equilibrium for concurrent force systems are obtained by
the applied forces
The forces acting on the free body are the action forces also called
experiment this one of the fundamental anxioms of mechanics
The parallelogram law cannot be proved it can only be demonstrated by
moment arm of the couple
The perpendicular distance between the action lines of the force is called the _____ their momentum is constant and independent of the moment center
non-coplanar
When the lines of action of all the forces in a forces them don't lie in one plane they are referred to as ______
coplanar.
When the lines of action of all the forces in a four system lie in one plane, they are referred to as being _____
The magnitude of the moment of a force
about an axis which is perpendicular to a plane containing the line of action of the force is defined as the product of the force of the perpendicular distance from the axis to the line of action of the force
Action and reaction forces
are equal but oppositely directed
The characteristics of a force
are it's magnitude the position of its line of action the direction or sense in which the force acts along the line of action
Solid bodies
are never rigid they deform under the action of Applied forces
The unit of force
commonly used in united states is the pound or multiples of the pounds such as the kip or ton.
