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4th Class Power Engineering Part A Exam/637 Q’s and A’s
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4th Class Power Engineering Part A Exam/637 Q’s and A’s
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4th Class Power Engineering PartA Exam/637 Q’s and A’s
Velocity (m/s) - -Change in position / time
-Acceleration (m/s^2) - -Change in velocity (m/s) / time (s)
-Force (Newton) - -mass (kg) x acceleration (m/s^2) , any action on a body
that tends to change its size, shape, or its state of rest or motion
-Force of Gravity - -mass (kg) x 9.81 m/s^2
-Pressure (Pa) - -Force (N) / area (m^2)
-Work (J) - -Force (N) x distance (m)
-Power - -Work done / time , Rate of doing work
-Potential Energy (J) - -mass x gravity x height , the ability of a body to do
work due by virtue of its position
-Kinetic Energy (J) - -1/2 x mass x velocity^2 , The ability of a body to do
work due to its motion
-Energy (J) - -The capacity of a body to do work
-Tonne - -1000 kilograms
-Moment of Force (Nm) - -Force (N) x Distance (m) , A force, acting on a
body at any distance from a point on that body, will tend to produce rotation
around that point
-Clockwise Moments - -Equal to Counter-clockwise moments
-Upward Forces - -Equal to Downward forces
-Actual Mechanical Advantage (Ma) - -Load (N) / Effort (N)
-Velocity Ratio (VR) - -Distance moved by Effort / Distance moved by Load
-Efficiency - -Output Work / Input Work
-Output Work - -Load x Distance moved by load
,-Input Work - -Effort x Distance moved by effort , Equals Output work +
Wasted work
-Ideal Mechanical Advantage (MA) - -Equal to Velocity Ratio (VR)
-Load x r - -Equal to Effort x R
-VR - -Equal to R/r and D/d
-Load /Effort - -Equal to R/r
-Scalar - -A physical quantity that has magnitude but no direction
-Vector - -A quantity that has magnitude and direction
-Space Diagram - -Illustrates a system of vectors
-Co-planar Vectors - -Vectors that are all in the same plane
-Concurrent Vectors - -Vectors whose lines of action meet at one point
-Resultant - -A vector that represents the sum of two or more vectors
-Absolute Pressure - -Atmospheric pressure + gauge pressure
-Static Friction - -A friction force that acts on objects that are not moving.
Always greater than kinetic friction
-Kinetic Friction - -Friction that opposes motion once the motion has already
started. Not affected by speed of body Always greater than rolling friction.
-Rolling Friction - -The friction force that acts on rolling objects, Always less
than kinetic friction
-Fluid Friction - -Friction that occurs as an object moves through a fluid
-Force of Friction - -Force that resists motion when two materials are in
contact. Proportional to the force that presses the two surfaces together. Not
affected by area. Affected by roughness.
-Elasticity - -The ability of a material to return to its original shape after
being disturbed
-Stiffness - -Ability of a material to resist a change in shape or size when a
load is applied
, -Plasticity - -Ability of a material to retain its deformed shape when a
deforming force is removed
-Ductility - -Ability of a material to be stretched and reduced in cross
section without breaking
-Toughness - -Ability of a material to absorb energy before breaking
-Hardness - -Ability of a material to resist penetration
-Stress - -Internal resistance to an external load , Equal to Load (N) / Area
(m^2)
-Tensile Stress - -Forces that act at opposite ends of a bar and pull away
from each other, creating tension on the bar
-Compressive Stress - -A stress due to a force pushing together on a body
-Shear Stress - -Forces on a bar that act parallel to another but are not on
the same plane
-Ultimate Stress - -The stress at which fracture of the material occurs
-Allowable Stress - -The greatest stress which a material is capable of
developing without permanent deformation remaining upon the complete
release of stress.
-Elastic Limit - -Maximum stress that a material will withstand without
permanent deformation. Will return to its original size and shape
-Factor of Safety - -Ultimate Stress / Allowable Stress
-Strain - -A measure of the deformation produced in a member by a load ,
Equal to Change in Length (l) / Original Length (L)
-Circumferance - -pi x Diameter
-Linear Speed - -Equal to rev/min x pi D / 60
-Four States of Matter - -solid, liquid, gas, plasma
-Phase - -One individual substance in one particular state
-Chemical Properties - -Only observed when there is a chemical change or
reaction , Examples are Heat of combustion, Toxicity, Flammability, Chemical
Stability
, -Physical Properties - -Characteristics that you can observe without a
change in the composition of matter
-Intensive Physical Property - -Not dependent on the amount of matter
-Extensive Physical Property - -Dependent on the amount of matter
-Mixture - -A combination of two or more substances that are not chemically
combined
-Homogeneous Mixture - -AKA Solution , Only has one set of properties ,
Possible only when all the components are in the same physical state , Ex.
Flue gas
-Heterogenous Mixture - -Non-uniform Composition , Substances may or
may not be in the same physical state , Ex. Oil and water emulsion , Sand
and water
-Matter - -Can be described in terms of its states, physical, and chemical
properties , State of matter is dependent on its temperature and pressure
-Pure Substances - -Elements and Compounds
-Atomic Number - -Represents the number of protons in an atom
-First Law of Thermodynamics - -The increase in internal energy of a closed
system is equal to the heat supplied to the system minus work done by it
(change in work=change in heat)
-Second Law of Thermodynamics - -Unaided, heat will flow only from a hot
substance to a colder substance
-Temperature - -A measure of the speed at which the body's molecules
vibrate (higher=higher speed)
-Heat - -Measure of the sum quantity of internal vibrational energy in a
substance
-Bimetal Thermometer - -Two dissimilar metals are rigidly fixed together
and will bend with temp. change due to their different coefficients of linear
expansion
-Pyrometer - -Measures temp. at the surface of an object
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