Statics Basics- Nohra 1-17
Mass
1) Scalar quantity 2) Amount of material in body 3) Measure of inertia (resistance to change in motion) 4) Same in any gravitational field (independent of location) 5) Units: slugs and kilograms; 1 slug = 14.59 kg.
gravity
9.81 m/s² or 32.2 ft/s²
Rigid Body
A mathematical model of a material body or a system of particles in which the distance between any two particles remains constant (no deformation)
Particle
A mathematical model of an object as a mass point. i.e. A particle has mass but no size (dimensions) or shape.
Newton's 2nd Law
F=ma When the sum of forces acting on an object is not zero, the sum of the forces is equal to the product of the mass and its acceleration.
Concurrent Forces
Forces that all intersect at a common point
Weight
W=mg (mass x acceleration due to gravity; 1 lb=4.448N)
Newton's 1st Law
When the sum of forces acting on an object is zero, the object will remain at rest if initially at rest.
Free-body Diagram
a diagram of a body or a group of bodies (or a part of a body) which is isolated from its environment and on which all external forces such as weight applied forces, reactions, moments, and friction are applied
External Force
a force acting on the outside of a structure set in equilibrium
Internal Force
a force effect within the entity or any component part of a structure set in equilibrium
Distributed Force
a force or force system spread over an area, either uniformly or non uniformly
Vector
a quantity (directed line segment) completely specified by mentioning magnitude and direction, and which add according to the parallelogram law ex: displacement, velocity, acceleration, momentum, force
Scalar
a quantity which can be completely specified without mentioning a direction. i.e. scalars have only a magintude ex: time, temperature, volume, mass, energy speed, distance
Newton's 3rd Law
a) The forces exerted by two objects on each other are equal in magnitude and opposite in direction. b) For every reaction there is an equal and opposite reaction.
Force
defined as that quantity which tends to change the state of motion of a body. This effect is physically felt as a push or pull. Characterized by point of application, magnitude, direction (on line of action)
Collinear Forces
forces acting along the same line of action
Coplaner Forces
forces that all lie on the same plane
Free vector
has a definite magnitude and direction but no specific location in space ex: the moment vector of a couple
General Space Force System
non-coplaner, non-parallel, non-concurrent, non-collinear force system
Magnitude
of a vector is nothing more than the length of the vector. Symbolized as |A|
Sliding vector
one which can be moved along a given line collinear with the vector itself ex: force causing rotation on a rigid body
Bound vector
one with a specific point of application ex: force acting on a deformable body; position vector
Moment
provides a measure of the tendency of a force to cause and object to rotate about a point or an axis M = Fd (scalar) or M = r x F (vector)
Concentrated Force
represents the effect of a loading which is assumed to act at a point on a body
Line of Action
the infinite straight line along which a force acts
