⚙️ Mechanical Eng Solved MCQs with Answers

Practice 934 approved ⚙️ Mechanical Eng questions with verified answers from the 🛠️ Engineering Essentials subject for Pakistan exams.

934 solved MCQs

If the air-fuel mixture ignites before the spark takes place at spark plug, the condition is calledAnswer: pre-ignition The information provided by the oxygen (O2) sensor to the feedback control system is about theAnswer: air-fuel ratio The diagram which shows the correct crank positions corresponding to the opening and closing of the valves, is known asAnswer: valve timing diagram The difference between DOT 3 and DOT 4 brake fluids isAnswer: DOT 4 fluid has a higher boiling point than DOT 3 fluid The battery is an electrochemical device, which means batteryAnswer: uses chemical action to provide electricity The operation of removing trapped air from the hydraulic braking system is known asAnswer: bleeding The aluminium alloy is used in cylinder blocks becauseAnswer: it is lighter and have good heat dissipation characteristics In a fuel injection system, the electronic control module (ECM) calculates the optimum fuel-injection volume for the engine condition based on the data received from the sensors, and injects this volume of fuel into the intake manifold at the optimum timing.Answer: Correct The tilting of the front wheels away from the vertical, when viewed from the front of the car, is calledAnswer: camber The main function of the tread pattern on tyre is thatAnswer: in wet conditions, the tread grooves expel water that is drawn between the tyre and road surface The neutral axis of the cross-section a beam is that axis at which the bending stress isAnswer: zero The compression ratio in petrol engine is kept less than in Diesel engine becauseAnswer: higher or equivalent compression ratio in petrol engines is not possible due to pre-ignition The most commonly used supplementary restraint system (SRS) component isAnswer: airbag The natural gas is compressed in a CNG cylinder at a pressure ofAnswer: 200 bar The cetane rating of Diesel fuel is in the order ofAnswer: 45 The air gap between the central electrode and ground (or side) electrode of a spark plug is aroundAnswer: 1 mm Euler's formula holds good only forAnswer: long columns The cetane number of a Diesel fuel is a measure ofAnswer: delay peirod The valve overlap in four stroke petrol engines is approximatelyAnswer: 30° The object of caulking in a riveted joint is to make the jointAnswer: leak-proof The petrol engines are also known asAnswer: spark ignition (S.I.) engines Which of the following indicates a multigrade oil ?Answer: SAE 20 W-50 A steel bar of 5 mm is heated from 15° C to 40° C and it is free to expand. The bar Will induceAnswer: no stress The coefficient of friction for the clutch facing is approximatelyAnswer: 0.4 A body is subjected to a tensile stress of 1200 MPa on one plane and another tensile stress of 600 MPa on a plane at right angles to the former. It is also subjected to a shear stress of 400 MPa on the same planes. The maximum normal stress will beAnswer: 1400 MPa The component that connects the steering rack to the knuckles isAnswer: tie-rod Two shafts 'A' and 'B' transmit the same power. The speed of shaft 'A' is 250 r.p.m. and that of shaft 'B' is 300 r.p.m. The shaft 'B' has the greater diameter.Answer: False Segmental chips are formed during machiningAnswer: cast iron Segmental chips are formed during machiningAnswer: cast iron The stress induced in a body, when suddenly loaded, is __________ the stress induced when the same load is applied gradually.Answer: twice