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IDIS 303 Exam 1 A
Terms in this set (81)
quantity of matter an object contains
size of gravity or amount of pulling force
push or pull; something that accelerates objects
_____ is the agent of change; _____ is the measure of change.
force acting on an object to cause a displacement
the effect of force acting at a specific distance from the axis of rotation. Measure of how much force is acting on an object causing it to rotate.
Torque is a ____ quantity.
the ability to do work. when work is done that system gains mechanical energy
the rate at which work is done. How fast work is done in a given time
Always calculated never measured
What measures horsepower?
Theoretical Mechanical Advantage
The factor by which it multiplies any applied force or torque.
AMA involves ____ and is therefore ____ than TMA.
measures the degree to which friction and other factors reduce the actual work output of the machine from its theoretical maximum.
the force that acts between two objects in contact because of action/reaction.
What is lost due to friction?
energy and power
Six Basic Machines:
Wheel and Axle
Three types of levers:
Type I: fulcrum in center with force pushing one end down
Type II: fulcrum on left with force pulling right up
Type III: fulcrum on right with force pulling center up
Wheel and Axle is what type of lever?
first class lever
Single fixed pulley has ___ mechanical advantage.
The mechanical advantage of an inclined plane is ____.
the length of the incline divided by the vertical rise
The mechanical advantage of a screw is a _____.
What is a pitch?
ratio of circumference to distance that the load advances in one revolution of a screw.
What type of engines are best for transportation and stationary industrial equipment?
internal combustion engines
External Combustion Engines
Internal Combustion Engine
Four strokes of Otto Cycle:
Intake, Compression, Power, Exhaust
When the piston is at the top of the chamber it is ____, at the bottom it is ____.
How many revolutions does a four stroke engine occur over?
region above piston at BDC and below it at TDC
Displacement in four stroke engines:
total swept volume of all cylinders
Piston rings are:
sliding seal between piston and cylinder to prevent leakage during compression
Why do engines not start?
Bad fuel mix
Lack of compression
Lack of spark
Three reasons why cars run on 4-strokes?
Easy to refuel
2-stroke engine combines the four strokes into:
Intake and Compression
Power and Exhaust
Diesel engines have a higher _____ and are more ____ than gasoline engines.
compression ratio; efficient
Diesel engines use ____ fuel injection while gasoline engines use ______ fuel injection or _____.
direct; port; carburetion
What happens in gasoline engines if too much air is compressed?
Diesel fuel is:
heavier and oilier since it takes less refining. Since it takes less refining it is cheaper.
higher energy density
Advantages of 2-stroke over 4-stroke:
simplified and lighter weight
they fire once a revolution rather than every other
orientation doesn't matter (4 must be upright)
Disadvantages of 2-stroke over 4-stroke:
shorter life since there is less lube
less efficient fuel use
lots of pollution
How does a gas turbine work?
burning of gas expands air which spins turbine
Advantages of gas turbine over diesel? Disadvantages?
good power-to-weight ratio
uses lots of fuel when idle
Outside heat source is used and no combustion occurs which makes the engine very quiet. Gasses never leave so no exhaust.
Used in submarines.
Two types of Stirling engines:
Displacer (1 piston, 1 displacer)
Two-Piston (2 pistons)
Wankel Rotary Engine:
Each stroke has its own housing with three separate volumes of gas.
Advantages and disadvantages of Wankel Engine over piston engines:
fewer moving parts
smoother since it continuously moves in one direction
slower which helps with reliability
higher manufacturing costs
consumes more fuel/lower compression ratio
Where must water be taken for steam engines?
must be taken at station since its constantly being lost in exhaust
Hybrid engine is essentially a ____:
electric car with a small horsepower engine that provides power once its at cruising speed.
Types of lubrication systems:
contact between shaft and bearing with thin film of lube in between. occurs during start-up
similar to boundary except some of load is now carried by hydrostatic pressure
a thick layer of lube in the bearing carries the load, no metal-to-metal contact
an external pump provides increased pressure on lube inside bearing (wind turbines)
____ additives used for heavily loaded gears where pressure between teeth squeeze out a standard.
EP (Extreme Pressure)
____ and ____ can be added during start up to make fluid film.
graphite and PTFE
Bearings use what for lubrication?
oil or grease. oil for roller bearings
Manual (Type A)
Constant (Type B)
Pressurized/Pumped (Type C)
Forms of lubrication:
Gaseous (He, Ar, CO2)
Solid (synthetic, metallic, mineral powders, coatings)
Liquid (fatty oils, mineral oils, synthetic oils)
Cohesive (paste, grease. waxes, soaps)
What is the most important property of lubrication?
When temperature decreases, viscosity should ____. When speed decreases, viscosity should ____.
What is the most widely used material for seals? Best for high temperatures? Best if water is present?
Nitrile; polyacrylites; silicone
Three types of drive tensioners (belts and chains)?
Three forms of flexible shafts:
Indexing drives are best for when:
parts must move from A to B quickly and repeatedly
What is a dwell?
when output is stationary and input is moving in a Geneva mechanism
How much of the total area between threads is metal to metal contact?
fill space and eliminate air paths that could cause leaks. makes machinery more reliable.
Most frequently used liquid lubrication?
petro-based or mineral oil
perpendicular to axis
Thrust loads (axial)
parallel to axis
limited to lighter loads and lower speeds. radial and thrust loads supported. low cost
Angular contact bearings
Can support high thrust loads and moderate radial loads.
support thrust loads and are either flat or grooved. grooved is most common
Four main categories of roller bearings:
have highest radial load capacity and speed capacity
can carry heavy radial loads in smaller space; low friction
support high radial loads and combined loads. self-aligning
support radial and axial loads. can tolerate some misalignment
can handle heavier loads and higher speeds at less friction and energy
applied in high speeds and support axial loads
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