4th Class Power Engineering Part A Exam
UPDATED QUESTIONS AND CORRECT
ANSWERS
Velocity (m/s) - CORRECT ANSWER Change in position / time
Acceleration (m/s^2) - CORRECT ANSWER Change in velocity (m/s) / time (s)
Force (Newton) - CORRECT ANSWER 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 - CORRECT ANSWER mass (kg) x 9.81 m/s^2
Pressure (Pa) - CORRECT ANSWER Force (N) / area (m^2)
Work (J) - CORRECT ANSWER Force (N) x distance (m)
Power - CORRECT ANSWER Work done / time , Rate of doing work
Potential Energy (J) - CORRECT ANSWER mass x gravity x height , the ability of a
body to do work due by virtue of its position
Kinetic Energy (J) - CORRECT ANSWER 1/2 x mass x velocity^2 , The ability of a
body to do work due to its motion
Energy (J) - CORRECT ANSWER The capacity of a body to do work
Tonne - CORRECT ANSWER 1000 kilograms
,Moment of Force (Nm) - CORRECT ANSWER 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 - CORRECT ANSWER Equal to Counter-clockwise moments
Upward Forces - CORRECT ANSWER Equal to Downward forces
Actual Mechanical Advantage (Ma) - CORRECT ANSWER Load (N) / Effort (N)
Velocity Ratio (VR) - CORRECT ANSWER Distance moved by Effort / Distance
moved by Load
Efficiency - CORRECT ANSWER Output Work / Input Work
Output Work - CORRECT ANSWER Load x Distance moved by load
Input Work - CORRECT ANSWER Effort x Distance moved by effort , Equals Output
work + Wasted work
Ideal Mechanical Advantage (MA) - CORRECT ANSWER Equal to Velocity Ratio
(VR)
Load x r - CORRECT ANSWER Equal to Effort x R
VR - CORRECT ANSWER Equal to R/r and D/d
Load /Effort - CORRECT ANSWER Equal to R/r
,Scalar - CORRECT ANSWER A physical quantity that has magnitude but no direction
Vector - CORRECT ANSWER A quantity that has magnitude and direction
Space Diagram - CORRECT ANSWER Illustrates a system of vectors
Co-planar Vectors - CORRECT ANSWER Vectors that are all in the same plane
Concurrent Vectors - CORRECT ANSWER Vectors whose lines of action meet at one
point
Resultant - CORRECT ANSWER A vector that represents the sum of two or more
vectors
Absolute Pressure - CORRECT ANSWER Atmospheric pressure + gauge pressure
Static Friction - CORRECT ANSWER A friction force that acts on objects that are not
moving. Always greater than kinetic friction
Kinetic Friction - CORRECT ANSWER Friction that opposes motion once the motion
has already started. Not affected by speed of body Always greater than rolling friction.
Rolling Friction - CORRECT ANSWER The friction force that acts on rolling objects,
Always less than kinetic friction
Fluid Friction - CORRECT ANSWER Friction that occurs as an object moves through
a fluid
, Force of Friction - CORRECT ANSWER 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 - CORRECT ANSWER The ability of a material to return to its original
shape after being disturbed
Stiffness - CORRECT ANSWER Ability of a material to resist a change in shape or
size when a load is applied
Plasticity - CORRECT ANSWER Ability of a material to retain its deformed shape
when a deforming force is removed
Ductility - CORRECT ANSWER Ability of a material to be stretched and reduced in
cross section without breaking
Toughness - CORRECT ANSWER Ability of a material to absorb energy before
breaking
Hardness - CORRECT ANSWER Ability of a material to resist penetration
Stress - CORRECT ANSWER Internal resistance to an external load , Equal to Load
(N) / Area (m^2)
Tensile Stress - CORRECT ANSWER Forces that act at opposite ends of a bar and pull
away from each other, creating tension on the bar
Compressive Stress - CORRECT ANSWER A stress due to a force pushing together on
a body
Shear Stress - CORRECT ANSWER Forces on a bar that act parallel to another but are
not on the same plane
UPDATED QUESTIONS AND CORRECT
ANSWERS
Velocity (m/s) - CORRECT ANSWER Change in position / time
Acceleration (m/s^2) - CORRECT ANSWER Change in velocity (m/s) / time (s)
Force (Newton) - CORRECT ANSWER 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 - CORRECT ANSWER mass (kg) x 9.81 m/s^2
Pressure (Pa) - CORRECT ANSWER Force (N) / area (m^2)
Work (J) - CORRECT ANSWER Force (N) x distance (m)
Power - CORRECT ANSWER Work done / time , Rate of doing work
Potential Energy (J) - CORRECT ANSWER mass x gravity x height , the ability of a
body to do work due by virtue of its position
Kinetic Energy (J) - CORRECT ANSWER 1/2 x mass x velocity^2 , The ability of a
body to do work due to its motion
Energy (J) - CORRECT ANSWER The capacity of a body to do work
Tonne - CORRECT ANSWER 1000 kilograms
,Moment of Force (Nm) - CORRECT ANSWER 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 - CORRECT ANSWER Equal to Counter-clockwise moments
Upward Forces - CORRECT ANSWER Equal to Downward forces
Actual Mechanical Advantage (Ma) - CORRECT ANSWER Load (N) / Effort (N)
Velocity Ratio (VR) - CORRECT ANSWER Distance moved by Effort / Distance
moved by Load
Efficiency - CORRECT ANSWER Output Work / Input Work
Output Work - CORRECT ANSWER Load x Distance moved by load
Input Work - CORRECT ANSWER Effort x Distance moved by effort , Equals Output
work + Wasted work
Ideal Mechanical Advantage (MA) - CORRECT ANSWER Equal to Velocity Ratio
(VR)
Load x r - CORRECT ANSWER Equal to Effort x R
VR - CORRECT ANSWER Equal to R/r and D/d
Load /Effort - CORRECT ANSWER Equal to R/r
,Scalar - CORRECT ANSWER A physical quantity that has magnitude but no direction
Vector - CORRECT ANSWER A quantity that has magnitude and direction
Space Diagram - CORRECT ANSWER Illustrates a system of vectors
Co-planar Vectors - CORRECT ANSWER Vectors that are all in the same plane
Concurrent Vectors - CORRECT ANSWER Vectors whose lines of action meet at one
point
Resultant - CORRECT ANSWER A vector that represents the sum of two or more
vectors
Absolute Pressure - CORRECT ANSWER Atmospheric pressure + gauge pressure
Static Friction - CORRECT ANSWER A friction force that acts on objects that are not
moving. Always greater than kinetic friction
Kinetic Friction - CORRECT ANSWER Friction that opposes motion once the motion
has already started. Not affected by speed of body Always greater than rolling friction.
Rolling Friction - CORRECT ANSWER The friction force that acts on rolling objects,
Always less than kinetic friction
Fluid Friction - CORRECT ANSWER Friction that occurs as an object moves through
a fluid
, Force of Friction - CORRECT ANSWER 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 - CORRECT ANSWER The ability of a material to return to its original
shape after being disturbed
Stiffness - CORRECT ANSWER Ability of a material to resist a change in shape or
size when a load is applied
Plasticity - CORRECT ANSWER Ability of a material to retain its deformed shape
when a deforming force is removed
Ductility - CORRECT ANSWER Ability of a material to be stretched and reduced in
cross section without breaking
Toughness - CORRECT ANSWER Ability of a material to absorb energy before
breaking
Hardness - CORRECT ANSWER Ability of a material to resist penetration
Stress - CORRECT ANSWER Internal resistance to an external load , Equal to Load
(N) / Area (m^2)
Tensile Stress - CORRECT ANSWER Forces that act at opposite ends of a bar and pull
away from each other, creating tension on the bar
Compressive Stress - CORRECT ANSWER A stress due to a force pushing together on
a body
Shear Stress - CORRECT ANSWER Forces on a bar that act parallel to another but are
not on the same plane
