Unit 1 Flashcards
Define force
An agent which when acts on a body, either produces or tends to produce change in state of a body
Action of one body on another, moves in the direction of action,
Characterised by magnitude, direction of action and point of application, its vector
Space
Geometric region occupied by bodies whose postions are described by linear and angular regions relatice to a coordinate system
Time
Measure of succesive events and is a basic quantity in dynamics, not directly involed in statics
Mass
Measure of inertia of a body, resistance to change of a velocity
Quantity of matter in a body, affects gravtitaional attraction
Particle
Body of negligable dimensions, itts dimensions are irrevalent
Rigid body
When change is distancw btw any 2 points is negligable
Free vector
Not fixed for a specific point in unique space can be anywhere
If body doesnt move with rotation direction of mag os same for all points
Sliding vector
Unique line of action in space, not unique point of application equal mag
Fixed vector
Unique point of application is specified , depends on mag, line of action
External and internal effects
External => reactive forces
Internal => resulting internal foces, deformatiknrs
Principal of transmissibility
Rigid body ignore deformations
“Force may be applied at any point on its given line of actiom without altering the resultant effects of the force external to rigid body on which it acts”
Contact and body forces
Contact => produced by direct contact
Body=> virtue of postion of body within a force field such as gravitation
Concurrent forces
If lines of forces intersect at that point
If they are applied at different points they move along line of action
Moment
the cross product of the position vector which runs from reference point to line of action of force
a force can tend to rotate a body about an axis, which neither intersects nor is parallel to the line of action of the force
Varignons Theorem
Moment of force about any point is equal to sum of moments of components of force about the same point
what is a couple
the moment produced by 2 equal, opposite and nonlinear forces
couple characteristics
net force of a couple is 0.
moment produced by a couple is same at any point.
can be balanced by an opposite couple or opposite moment.
not be replaced by a single force.
why does moment doesnt change for a couple when you change the centre
total moment is the same no matter the moment center.
when you shift the moment center, both forces shift together, and their combined effect (the rotation) remains unchanged.
resultant
the simplest force combination which can replace the original forces without altering the external effect on the rigid body to which the forces are applied.
equilibrium
resultant of all forces acting on the body is zero. = in statics. When the resultant of all forces on a body != zero, acceleration => force resultant = m*a of the body. => in dynamics.
both in statics and dynamics.
