Download PE 3rd Class A1 Exam Questions with Complete Solutions and more Exams Engineering in PDF only on Docsity!
PE 3rd Class A1 questions with
complete solutions graded A+
- In a right angle triangle, the sine of an acute angle is equal to: - correct answer ✔✔opposite side / hypotenuse If a right-angle triangle has an angle of 28O 37' and the hypotenuse is 120 mm, the length of the opposite side is: - correct answer ✔✔57.48 mm In the equation 0.004 + D = 0.0042, the value of D is: - correct answer ✔✔0. As the cosine decreases, the - correct answer ✔✔value of the angle increases Any two angles whose sum is 90° are: - correct answer ✔✔complementary angles One is the trigonometric value of: - correct answer ✔✔A. sine of 90° B. cosine of 0° C. tangent of 45° A automobile travels at 60 miles per hour. Expressed in metres per second, this would be equivalent to: - correct answer ✔✔26.81 m/s The force that is equal in magnitude but opposite in direction to the resultant force is called: - correct answer ✔✔the equilibrant A scalar quantity is one which has only magnitude and can be fully described by: - correct answer ✔✔a number with the necessary unit A body can be put into equilibrium by applying an additional force equal in magnitude but opposite in direction to the: - correct answer ✔✔resultant
A displacement of 9 m north of point A, and another of 6 m west of point A can be added to give a resultant displacement from point A of: - correct answer ✔✔10.8 m N of W The moment of a force about a point is: - correct answer ✔✔a twisting or turning effect When the co-efficient of friction increases and the force between two surfaces remains constant, the friction force will: - correct answer ✔✔increase A body having a gravitational force of 2000 N, is pulled along a horizontal surface at constant speed by a rope that makes an angle of 20° above the horizontal. If the pull on the rope is 150 N, the coefficient of sliding friction is: - correct answer ✔✔0. Energy can be: - correct answer ✔✔transformed to different forms Velocity ratio is: - correct answer ✔✔ideal mechanical advantage A 1 N weight has a kinetic energy of 1 J when its speed is: - correct answer ✔✔4. m/s The working stress of a material that has an ultimate strength of 490 MPa and a safety factor of 7 would be: - correct answer ✔✔70 MPa According to Hooke's Law, the stress in an elastic body is directly proportional to the strain if: - correct answer ✔✔the elastic limit of the material is not exceeded The factor of safety is always expressed: - correct answer ✔✔as a ratio When calculating the ultimate stress of a material, we should: - correct answer ✔✔divide the maximum load by the original cross-sectional area
0 °C to 124 °C is: - correct answer ✔✔520.72 kJ/kg When heat is supplied to a liquid in sufficient quantity to change the liquid to a vapour without changing the temperature, the heat supplied is known as: - correct answer ✔✔latent heat of evaporation The dryness fraction of steam at a pressure of 400 kPa and a heat content of 2500 kJ/kg is: - correct answer ✔✔0. The temperature of saturated steam vapor at 980 kPa is: - correct answer ✔✔179. °C Steam engines, steam turbines, gas turbines and internal combustion engines are examples of: - correct answer ✔✔heat engines The rate at which heat flow through a slab of a material does not depend on: - correct answer ✔✔the specific heat of the material Expansion of a gas is said to be adiabatic when expansion takes place at : - correct answer ✔✔falling temperature If 10 m3 of a gas at a pressure of 20 kPa (gauge) and a temperature of 10 °C are compressed to 5 m3 while the temperature is reduced to -20 °C, the final gauge pressure will be: (Consider the atmospheric pressure to be 95 kPa) - correct answer ✔✔110.6 kPa Use of the equation PV = a constant, means the numerical result of pressure times volume for a compression or expansion process will: - correct answer ✔✔be the same at any point in the process A gas occupies 8.62 m3 at 1800 kPa and 26 °C. It is heated until the final volume is 9.0 m3 and pressure is 2500 kPa. the final temperature will be approximately: - correct answer ✔✔ 161 °C
H2SO4 is the chemical formula for: - correct answer ✔✔sulfuric acid Protons have a mass number of: - correct answer ✔✔One A pinch of salt is added to a glass of water. The result is: - correct answer ✔✔a solution Compounds classified as salts may have the following characteristics: - correct answer ✔✔1. have a basic effect
- have an acid effect
- be neutral
- change red litmus paper blue The most common material used in making large industrial diesel engine pistons is:
- correct answer ✔✔Cast iron Malleable cast iron is produced by: - correct answer ✔✔heating and cooling white cast iron at a controlled rate Steam turbine bearings are usually made of: - correct answer ✔✔white metal and bronze The most common thread used in North America on fasteners such as bolts, is the: - correct answer ✔✔Unified National Orthographic projection means: - correct answer ✔✔view of a cutting plane The classes of fastening devices are: - correct answer ✔✔permanent and removable Naperian (Natural) logarithms - correct answer ✔✔is a number that appears naturally in some higher-level mathematics is 2.71828 (correct to 5 decimal places)
Trapezium - correct answer ✔✔a quadrilateral with no parallel sides polygon - correct answer ✔✔a closed plane figure bounded by straight sides hexagon - correct answer ✔✔a polygon with 6 sides A = 0.433s2 for equilateral triangle
- therefore a hexagon A = 6 x 0.433s2 or A = 2.6s octagon - correct answer ✔✔all sides equal, all angles are equal and opposite sides parallel divided into 6 ISOSCELES triangles, each angle in an octagon is 135 A = 4.83s areas of sectors (bounded by 2 radii and arc between them) - correct answer ✔✔A = arc length x radius / 2 A = (pi/360) x pir length of radii and angle between radii known area of a segment - correct answer ✔✔a "chord" is a straight line that joins 2 points or circumference A = 4/3h2 [(square root)d/h-0.608] ellipse - correct answer ✔✔a closed plane curve resulting from the intersection of a circular cone and a plane cutting completely through it A = piab or A = pi(1/2D)(1/2d) - same as = (pi/4)D/d coefficient of friction - correct answer ✔✔the ratio of the weight of an object being moved along a surface and the force that maintains contact between the object and the surface
- u = tan(thada)
- coefficient of friction is equal to the tangent of friction angle
force - correct answer ✔✔mass x acceleration (N) work - correct answer ✔✔force(N) x distance(m) or W=Fd o unit of joules o 1KJ = 1000J = 1000Nm = 1KNm o 1MJ = 1000000J = 1000000NM = 1MNm power - correct answer ✔✔= work done(J)/time(second) o unit of watts o 1 watt = 1 joule/second mechanical efficiency - correct answer ✔✔= output power(W)/input power(W) problem solving order - correct answer ✔✔o force o work done o power o mechanical efficiency stroke - correct answer ✔✔the total direction traveled by the piston within a cylinder power stroke - if pressure is being applied during the stroke effective pressure - correct answer ✔✔indicated the pressure that should be used when calculating power pressure is not constant throughout a power stroke decreases as gas/steam expands power from an engine can be calculated: - correct answer ✔✔o Pm = mean effective pressure (Pa) o A= area of piston (m2) o L= length of stroke (m) o N= number of power strokes per second
factor of safety - correct answer ✔✔= ultimate stress/working stress continuity flow - correct answer ✔✔in a pipe if no fluid is added or removed o flow must remain constant o due to the product of area and velocity being constant o flow must be the same going in as coming out of pipe relative density - correct answer ✔✔- the ratio of the density of a substance to the density of a standard substance at the same temperature and pressure
- the ratio of the density of the substance to the density of the substance to the density of water specific heat - correct answer ✔✔is the amount of heat/energy required to increase or decrease the temperature of any given substance's unit mass 1 degree Celsius
- unit in joules
- factors that determine amount of heat transfer
- mass
- specific heat
- change in temp of substance sensible heat - correct answer ✔✔is the heat being added or removed to/from a substance without a change of state, still having a changing in temp latent heat of evaporation (vaporation) - correct answer ✔✔is the required to change a unit mass from a gas to liquid or liquid to a gas specific heat - correct answer ✔✔'quantity of heat required to change the temp of a unit mass of a substance by 1 degree' total heat required for change of state - correct answer ✔✔- total heat = sensible heat + total latent heat
- mc(specific heat) x delta t + mLf/mLe
- Lf = latent heat of fusion
- Le = latent heat of evaporation Calorimetry - correct answer ✔✔the precise measurement of heat flow out of a system for chemical and physical processes water equivalent - correct answer ✔✔is 'the equivalent mass of water that would require the same amount of heat transfer as the substance, to produce the same temp change coefficient of expansion - correct answer ✔✔a Greek letter alpha linear coefficient of superficial (area) expansion - correct answer ✔✔gamma
- coefficient of superficial = 2x coefficient of linear expansion coefficient of volumetric expansion - correct answer ✔✔- coefficient of cubical expansion is often used instead of 'volume' -coefficient of liquids only dryness fraction - correct answer ✔✔the parts/fraction of steam that is dry is called dryness fraction o expressed as a fraction, percentage or decimal Boyle's law - correct answer ✔✔The relationship between the pressure and volume of a gas at constant temperture; when volume increase, pressure decreases. Charles Law - correct answer ✔✔the law that states that for a fixed amount of gas at a constant pressure, the volume of the gas increases as the temperature of the gas increases and the volume of the gas decreases as the temperature of the gas decreases General gas law - correct answer ✔✔PV=nRT - Boyle's law and Charle's law combined
o suitable for case hardening o resistance to wear and abrasion benefits of chromium - correct answer ✔✔o resists oxidation o high strength at high temperatures o increases hardness and abrasion resistance without increasing brittleness o increases response to heat treatment o increases depth of hardness penetration o at 12% chromium steel with not tarnish benefits of copper - correct answer ✔✔o combines easily with many other elements o improves atmospheric corrosion resistance o increases strength o amounts of 0.15-0.25% hardness - correct answer ✔✔resistance to wear, abrasion and penetration malleability - correct answer ✔✔ability to withstand deformation above elastic limit under compression without failure toughness - correct answer ✔✔whether a material will break under sudden impact or hard blow elasticity - correct answer ✔✔the ability to return to its original shape after an external force has been removed stray current corrosion - correct answer ✔✔aka stray current electrolysis o caused be an external source of current o non intended paths due to poor electrical conductor
stress corrosion cracking - correct answer ✔✔dangerous because a crack starts slowly and propagate slowly o exceed breaking strength and the metal fails suddenly o stress must be tensile can be produced by an external load or residual stress o condensed moisture and change in temperature copper fails due to - correct answer ✔✔ammonia stainless fails due to - correct answer ✔✔chlorides conditions required to produce sulphide corrosion cracking - correct answer ✔✔o moist hydrogen sulphide environment o hydrogen sulphide must be present o water, even trace amount o high strength steel o steel must be under tensile stress, either applied or residual micro organisms promote corrosion - correct answer ✔✔o "under deposit corrosion" o"enhanced oxygen generation" - contactof live organisms cathodic protection system - correct answer ✔✔negative terminal of the rectifier must always be connected to the structure that is being protected PFDs - correct answer ✔✔process flow drawing P & IDs - correct answer ✔✔mechanical flow diagrams purpose of P & IDs - correct answer ✔✔o pre-construction, shows graphically the mechanical design engineer's work o during construction, proper location, reference to all equipment
