Characteristics of a Force
What is an example of a colinear system?
One intelligent hiker observing three other hikers dangling from a rope
What is a force characterized with?
Point of application, Direction, and magnitude
What is the magnitude?
Refers to the quantity of force; a numerical measure of its intensity. Basic units of force are the pound (lb) and kip or K (K=1000lb)
What concept are the equations of equilibrium in statics based on?
Rigid Bodies
What is the Principle of Transmissibility?
The external effects on a body (i.e. a truss) remain unchanged when a force F acting at point A is replaced by a force F of equal magnitude at point B, provided that both forces have the same direction (sense) and line of action
What is newton's second law of motion?
The time rate of change of momentum (m * v/t or m *a) is equal to the force, F, producing it (F=m*a). The change takes place in the direction the force is acting
What are the external forces and internal forces of a column on a footing in the ground?
The weight of the column itself and the weight of the footing itself are external forces and the resistance of the soil against the footing which the column is on is an internal force
What are vectors?
`Quantities of magnitude AND direction with rules of addition
What is an external force (F)?
a force exerted on a system or a component of the system from a part outside the system. Sometimes referred to Applied forces (i.e. a hammer pulling on the nail)
What are forces?
a result of gravity induced loads (structure/material weights, occupancy loads), wind pressures, and inertial loads from earthquakes
What is a rigid body?
a structural element displaying negligible or no noticeable deformation under a load
What is force?
that action of one body on another that affects the state of motion or rest of the body
What is an internal force (R)?
the force which hold an object together when an external force is applied. Internal forces are sometimes called resisting forces since they resist the effects of external forces (i.e. the embedded potion of the nail resists the external force through frictional resistance)
What is the point of application?
the point where the force is applied
What is an example of a coplanar parallel system?
A beam supported by a series of columns
What is a coplanar system?
All forces acting along the same plane
What is a colinear system?
All forces acting along the same straight line
What is a coplanar parallel system?
All forces are parallel and act in the same plane
What is a coplanar concurrent system?
All forces intersect at the same point and lie on the same plane
What is newton's first law of motion?
Any body at rest will remains in rest and any body in motion will move uniformly in a straight line unless acted upon by a force (equilibrium)
How are forces depicted in free body diagrams?
As vectors
What are the different types of systems that a system of forces may act on?
Collinear, Coplanar Parallel, Coplanar Concurrent, non-coplanar parallel, non-coplanar concurrent, non-coplanar non-concurrent
What are deformable bodies?
Elements that are subject to large deformations under a load. Precursor to "Strength of Materials"
What is newton's third law?
For every force of action, there is a reaction that is equal in magnitude, opposite in direction, and has same line of action
What is an example of a coplanar system?
Forces acting in a buttress system
What is the direction of a force defined as?
Its line of action and sense. The line of action represents an infinite straight line along which the force is acting
What is an example of a coplanar concurrent system?
Loads applied to a roof truss