firstexam Flashcards
A machine is something that ____ force
modifies
____ is when force comes from an outside source
Input
The mechanical action of the machine produces _____
output
The study of the motions and forces that occur between input and output
Mechanics
First Law of Mechanics
Motion does not require force; force only needed to accelerate motion
Second Law of Mechanics
The greater the force, the greater the acceleration
Third Law of Mechanics
Action and Reaction; of object pushed, it will push equally in opposite direction
5 basic mechanical systems
Inclined plane, wedge, screw, lever, wheel
Lever of first order
Fulcrum is always between load and effort
Lever of second order
Load lies between fulcrum and effort
Lever of third order
Effort applied between fulcrum and load
Shaft and bearing
Shafts can be anything, they must fit bearings which keeps the rotating shaft stable and running smoothly
Snail Cam
Pushes shaft upwards; shaft also needs support of a bearing;
Crank
A lever attached to a rotating shaft - converts rotation to reciprocation; crank is circular disk with pin, rod constrained by guides, when shaft rotates, rod reciprocates
Cams turn_____ motion into an upward and downward motion
rotary
Lobe cams
Produce multiple events per cycle
All machines almost always employ at least _____
one lever
Mechanical ______ is ratio of load versus effort
advantage
Leverage is the ratio distances of the ____and load to the fulcrum
effort
A lever of the second order is also known as a force _____
multiplier
A lever of the third order is also known as a force _____
reducer
A ______converts rotation to reciprocation
lever attached to a rotation shaft-cranks
____is the difference between a cam’s minimum and maximum radii
Throw
Eccentricity
Means to be off-center; like a cam
Unlike cranks, cams have the ability to store _______
information
Cams are the ______version of computer programs
mechanical
A ____ crank converts up-down motion to side-to-side motion
bell
A 3-bar linkage is for _____motion
straight-line
A slider-crank with a _____increases lever sway
lower bearing
Levers move in a ______arc
circular
A _____can be used to keep the lever against the cam so it follows the profile
spring
Springs in cam-followers increase _____, so tensioners are used
friction
4 types of springs
compression, extension, torsion, and radial springs
Ratchets give ____motion
stepped
For ratchets, the ______ stops the wheel from slipping back
second pawl (detent)
Drives and gearing provide _____ connections
rotary-to-rotary
In friction drives, _____is often employed to prevent belt slip
flanges
A _____ is a tensioning mechanism which is used to take up slack in a belt
tensioner
In timing belts, the belt has ____ to engage the notches in the pulley wheels
teeth
In chain and sprocket drives, ____ can be added or removed
links
Spur gears have the same number of ____
teeth
In a _____drive, the geared wheel meshes with a toothed rack
rack and pinion
In a _____drive, the geared wheel meshes with a toothed rack
worm gear
In bevel gears, the 2 wheels mesh at ____degrees
45
The _____is simpler form of the bevel gear and is easier to fabricate
pin wheel
In bevel gears, the _____changes from horizontal to vertical
plane of rotation
Two types of positive drives
Toothed Belts and Chain&Sprocket
Two types of drives
Friction and positive; positive have input and output locked and synchronous while friction use friction to transfer movement
Bevel gear changes the plane of rotation from ______ to _____
horizontal to vertical
