4th Class Power Engineering Part A Exam
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
4TH CLASS POWER ENGINNERING CLASS A EXAM
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
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
4TH CLASS POWER ENGINNERING CLASS A EXAM
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
