4th Class Power Engineering Part A Exam Verified Solutions

4th Class Power Engineering Part A Exam Verified Solutions 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