4th Class Power Engineering Part A Exam Study Guide with Complete Solutions 2024/2025 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 1 / 4
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 2 / 4
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 3 / 4
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 Ultimate Stress - Correct Answer The stress at which fracture of the material occurs Allowable Stress - Correct Answer The greatest stress which a material is capable of developing without permanent deformation remaining upon the complete release of stress.Elastic Limit - Correct Answer Maximum stress that a material will withstand without permanent deformation. Will return to its original size and shape Factor of Safety - Correct Answer Ultimate Stress / Allowable Stress Strain - Correct Answer A measure of the deformation produced in a member by a load , Equal to Change in Length (l) / Original Length (L) Circumferance - Correct Answer pi x Diameter Linear Speed - Correct Answer Equal to rev/min x pi D / 60
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