Forces Moments and Equilibrium Flashcards
What does a Force Mean?
Measure of a tendency to cause a body to move in the direction of that force
Defined by its magnitude and direction (vector)
Name the main 2 forms of applied force in a cantilever beam
Point loads (concentrated at 1 point)
Distributed load. (every point of the beam experiences the same force for a set distance)
What is a moment?
Define the magnitude of a moment.
measure of a forces tendency to cause a body to rotate about a specific point or axis
Product of the force and the perpendicular distance between the line of action and the lever arm
Name the 3 support types in FBD
Roller, pinned, Fixed
What’s the difference between a Pin , Roller and Fixed Connection.
Roller only restrains the y displacement caused by the force (or only 1 reaction force)
Pin restrains both the x & y displacement (or only 2 reaction forces)
Fixed restrains x , y displacement and rotation of the beam. (2 forces and 1 moment)
(If a connection restricts a displacement or a rotation, it provides internal force opposite to the external force. )
(If a connection doesnt restrict, it doesnt provide an internal force to oppose the external force)
What to FBD show?
External Forces acting on an isolated body
Draw the Isolated FBD
Draw the Isolated FBD
Draw the Isolated FBD
Draw the Isolated FBD
Draw the Isolated FBD
Draw the Isolated FBD
Draw the Isolated FBD
Draw the Isolated FBD
Draw the Isolated FBD
What are the conditions for equilibrium
Sum of Reaction and External forces = 0
Sum of Reaction and External moments = 0
Calculate the Magnitudes of the Reactions
1) Draw FBD
2) Resolve X , Resolve Y
3) Resolve moment about point
4) Sub in
Calculate the magnitude of the reactions
1) Isolate Free Bodies, (Small wheel , Large Wheel & Frame)
2) Draw 3 FBD .
3) Resolve FBD of small wheel to find roller support forces.
4) Resolve FBD of large wheel to find Pin support forces.
5) Resolve FBD of frame to find pin & roller support forces.
What is a statically determinate problem?
What is a Statically Indeterminate Problem
Static - In a equilibrium state
We only require to solve equilibrium equation to find reaction of the supports
We require more then just equilibrium to solve for reaction.
What are the reaction forces?
What are the reaction forces
Prove that the following is Statically Determinate
DOI > 0 = Statically Indeterminate
DOI = 0 = Statically determinate
DOI(trusses) = External + Internal Unknowns - 2(number of connections)
Probe that the following is statically determinate
DOI > 0 = Statically Indeterminate
DOI = 0 = Statically determinate
DOI (FBD) = (External + Internal Unknowns) - 3(Number of FBD used to split it up)
