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# POE Unit 2 Key Terms

### O'Connor's POE Unit 2 Key Terms

Term | Definition |
---|---|

Cable | A strong rope, usually made of metal, designed to have great tensile strength and to be used in structures. |

Centroid | The geometric center of an area. |

Compression Force | A body subjected to a push. |

Concurrent Force Systems | A force system where all of the forces are applied at a common point on the body or having their lines of action with a common intersection point. |

Cross-Sectional Area | A surface or shape exposed by making a straight cut through something at right angles to the axis. |

Direction | The direction of a vector is defined by the angle between a reference axis and the arrow’s line of direction. |

Fixed Support | A support that prevents translation and rotation in a beam. |

Flange | A broad ridge or pair of ridges projecting at a right angle from the edge of a structural shape in order to strengthen or stiffen it. |

Free Body Diagram | A diagram used to isolate a body from its environment, showing all external forces acting upon it. |

Gusset | A plate or bracket for strengthening an angle in framework. |

Joint | The connection points of members of a truss. |

Magnitude | The absolute value of a number. |

Member | Slender straight pieces of a truss connected by joints. |

Method of Joints | A method of analysis of trusses which constructs free body diagrams of each joint and determines the forces acting in that joint by considering equilibrium of the joint pin. |

Moment | The turning effect of a force about a point equal to the magnitude of the force times the perpendicular distance from the point to the line of action from the force. |

Moment of Inertia | A mathematical property of a cross section that is concerned with a surface area and how that area is distributed about a centroidal axis. |

Newton’s First Law | Every body or particle continues at a state of rest or uniform motion in a straight line, unless it is compelled to change that state by forces acting upon it. |

Newton’s Second Law | The change of motion of the body is proportional to the net force imposed on the body and is in the direction of the net force. |

Newton’s Third Law | If one body exerts a force on a second body, then the second body exerts a force on the first body which is equal in magnitude, opposite in direction, and collinear. |

Pinned Support | A support that prevents translation in any direction. |

Planar Truss | A truss that lies in a single plane often used to support roofs and bridges. |

Resultant Force | The resultant of a system of force is the vector sum of all forces. |

Roller Support | A support that only prevents a beam from translating in one direction. |

Scalar | A physical quantity that has magnitude only. |

Sense | The sense of a vector is the direction of the vector relative to its path and indicated by the location of the arrow. |

Simple Truss | A truss composed of triangles, which will retain its shape even when removed from supports. |

Static Equilibrium | A condition where there are no net external forces acting upon a particle or rigid body and the body remains at rest or continues at a constant velocity. |

Statically Indeterminate | A structure or body which is over-constrained such that there are more unknown supports than there are equations of static equilibrium. |

Structure | Something made up of interdependent parts in a definite pattern of organization, such as trusses, frames, or machines. |

Tension Force | A body subjected to a pull. |

Vector Quantity | A quantity that has both a magnitude and direction. |