Exam 2 Flashcards
When is a body in equilibrium?
When it isn’t accelerating
What is the net force and moment on body in equilibrium
Both are zero
How does ‘neglecting friction’ change the forces acting on an object?
Only the force perpendicular to the object remains
What kind of forces are created by a flexible cable, belt, chain, or rope?
A tension away from the body in the direction of the cable
What kind of forces are created by a smooth surface
One contact force that is normal to the surface
What kind of forces are created by rough surfaces
A resultant force made of both frictional (x) and normal (y) components
What kind of forces are created by roller supports
One normal force
What kind of forces are created by a freely sliding guide?
A force normal to the guide only
What kind of forces are created by a pin connection?
A pin that is free to turn has a resultant force with x and y components.
What kind of forces are created by a built-in or fixed support?
An axial (x) force and a shear force (y) and a couple M to prevent rotation
What do pulleys do?
Pulleys permit a friction-free change in direction of a force
If a pulley system is in equilibrium, what can be said about the tension?
Both sides of a cable/rope passing over a pulley will be under the same tension
What is a two-force member?
A member with only 2 points where forces are acting, no couple or reaction momemnt, and negligible weight
What does it say about the forces if a member is a two-force member?
The forces at those 2 points have to be equal, opposite, and along the line joining those two points
What 6 equations can you use for a body that is in 3D equilibrium?
Fx, Fy, Fz, Mx, My, Mz
