Mechanical Engineering Question Bank

Bangladesh Industrial Technical Assistance Centre (BITAC)- 2026

Post: Assistant Engineer (Mechanical)

Exam Date: 24.04.2026 Exam Hall: BUTEX

Time: 1 Hour 30 Min Total Marks: 80 (Departmental 50, Bangla 10, English 10, GK 10)

Question Prepared by: BITAC

Departmental:

1) A room wall 400 mm thick is made of a material having thermal conductivity of 1 W/m·K. The inner and outer surfaces are exposed to average temperatures of 20°C and 0°C respectively. If the inner and outer air film coefficient is 0.5 W/m²·K, find the heat flux. [5]

Solution: Q9, QB-162, Dhaka Power Distribution Company Limited (DPDC)-2019.

$q = \frac{T _{i} - T _{o}}{\frac{1}{h _{i}} + \frac{L}{k} + \frac{1}{h _{o}}} = \frac{20 - 0}{\frac{1}{0.5} + \frac{0.4}{1} + \frac{1}{0.5}} = \frac{20}{4.4} = 4.55 W/m^{2}$

2) The actual discharge of a single-acting reciprocating pump is 0.02 m³/s when running at 55 rpm. The length of the stroke is 500 mm and the diameter of the cylinder is 250 mm. For a total static head of 16 m, calculate the percentage slip, the coefficient of discharge and the theoretical power required to drive the pump. [5]

Solution: $A = \frac{π}{4} (0.25)^{2} = 0.04909 m^{2}, Q_{t h} = \frac{A L N}{60} = \frac{0.04909 \times 0.5 \times 55}{60} = 0.0225 m^{3} / s$

$% Slip = \frac{0.0225 - 0.02}{0.0225} \times 100 = 11.1%, C_{d} = \frac{0.02}{0.0225} = 0.889$

$P_{t h} = ρ g Q_{t h} H = 1000 \times 9.81 \times 0.0225 \times 16 = 3531 W = 3.53 kW$

∴ Slip = 11.1%; C_d = 0.889; Theoretical power = 3.53 kW (Answer)

3) A counter flow shell-and-tube heat exchanger cools water from 60.2°C to 30.5°C by ethylene glycol entering at 4°C. The specific heats of water and ethylene glycol are 4200 J/kg·K and 3330 J/kg·K, and their mass flow rates are 6.1 kg/s and 5.6 kg/s respectively. Find the LMTD. [5]

Answer: Q2, QB-147, Ashuganj Power Station Company Limited (APSCL)-2019.

4) In an air-standard Brayton cycle, air enters the compressor at 0.5 MPa and 15°C and leaves at 1.5 MPa. The maximum temperature is 1000°C and the compressor efficiency is 85%. Take γ = 1.4, c_p = 1.004 kJ/kg·K and c_v = 0.717 kJ/kg·K. Find the compressor work. [5]

Answer: Q4, QB-148, Ashuganj Power Station Company Limited (APSCL)-2019.

5) A 1 m long bar of rectangular cross-section 10 mm × 5 mm carries an axial tensile load of 7000 N. Find the principal stresses and the maximum shear stress. [5]

Solution: Q10, QB-146, Ashuganj Power Station Company Limited (APSCL)-2019.

$σ_{1} = \frac{7000}{10 \times 5} = 140 MPa, σ_{2} = 0, τ_{m a x} = \frac{σ _{1}}{2} = 70 MPa$

6) Derive the expression for the elongation of a bar hanging vertically under its own weight, having length L, mass m, cross-sectional area A and modulus of elasticity E. [5]

Solution:

Bar hanging vertically under its own weight with element dy at distance y from the free end

Consider an element of length dy at a distance y from the free (lower) end. The weight of the bar below this section is

$P_{y} = \frac{W}{L} y = \frac{m g}{L} y$

Elongation of the element:

$d δ = \frac{P _{y} d y}{A E} = \frac{m g}{A L E} y d y$

Total elongation:

$δ = \int_{0}^{L} \frac{m g}{A L E} y d y = \frac{m g}{A L E} \times \frac{L ^{2}}{2} = \frac{m gL}{2 A E} = \frac{W L}{2 A E} = \frac{ρ g L ^{2}}{2 E}$

Thus the elongation due to self-weight is half of that produced by the same weight applied at the free end.

7) Elaborate the following terms: NPSH, EDM, AHU, BHP and ASHRAE. [5]

Solution: NPSH — Net Positive Suction Head; EDM — Electrical Discharge Machining; AHU — Air Handling Unit; BHP — Brake Horsepower; ASHRAE — American Society of Heating, Refrigerating and Air-Conditioning Engineers.

8) A hollow steel tube with an inside diameter of 100 mm must carry a tensile load of 400 kN. Determine the outside diameter of the tube if the stress is limited to 120 MN/m². [5]

Solution: $A = \frac{P}{σ} = \frac{400 \times 1 0 ^{3}}{120} = 3333.3 mm^{2} = \frac{π}{4} (D_{o}^{2} - 10 0^{2})$

$D_{o}^{2} = 10 0^{2} + \frac{4 \times 3333.3}{π} = 14244 \Rightarrow D_{o} = 119.35 mm$

∴ Outside diameter = 119.35 mm (say 120 mm) (Answer)

9) A gear train has three gears: gear A (20 teeth, driver), gear B (40 teeth, idler) and gear C (80 teeth, driven). Find the overall gear ratio between A and C. [5]

Solution: $\frac{N _{A}}{N _{C}} = \frac{N _{A}}{N _{B}} \times \frac{N _{B}}{N _{C}} = \frac{T _{B}}{T _{A}} \times \frac{T _{C}}{T _{B}} = \frac{T _{C}}{T _{A}} = \frac{80}{20} = 4$

The idler does not affect the gear ratio; it only changes the direction of rotation, so gear C rotates in the same direction as gear A.

∴ Overall gear ratio = 4 : 1 (Answer)

10) An open tank contains water up to a depth of 2 m and above it an oil of specific gravity 0.9 for a depth of 1 m. Find the pressure intensity at the interface of the two liquids. [5]

Solution: $p = ρ_{o i l} g h_{o i l} = 900 \times 9.81 \times 1 = 8829 N/m^{2} = 8.83 kPa (gauge)$

(Pressure at the bottom = 8829 + 1000 × 9.81 × 2 = 28,449 N/m².)

∴ Pressure at the interface = 8.83 kPa (gauge) (Answer)

বাংলা:

11) বাংলা ভাষায় ব্যবহৃত মৌলিক স্বরধ্বনি কয়টি এবং কী কী?

উত্তর: ৭টি — অ, আ, ই, উ, এ, ও, অ্যা।

12) ‘পুষ্পসৌরভ’ কোন সমাসের উদাহরণ?

উত্তর: ষষ্ঠী তৎপুরুষ সমাস (পুষ্পের সৌরভ)।

13) (ক) সন্ধি করুন: পর + উপকার (খ) সন্ধি বিচ্ছেদ করুন: উদ্যোগ

উত্তর: (ক) পরোপকার (খ) উৎ + যোগ।

14) (ক) ‘পরিশ্রম করলে সাফল্য আসে’ — জটিল বাক্যে রূপান্তর করুন। (খ) ‘সে অত্যন্ত ধীরে ধীরে কথা বলছিল।’ — ‘ধীরে ধীরে’ কোন পদ?

উত্তর: (ক) যদি পরিশ্রম কর, তবে সাফল্য আসবে। (খ) ক্রিয়া বিশেষণ।

15) ‘বিদ্রোহী’ কবিতা কোন কাব্যগ্রন্থের অন্তর্গত?

উত্তর: অগ্নিবীণা (কাজী নজরুল ইসলাম)।

English:

16) Use the correct verb forms to fill in the gaps: Either the senior executives or the CEO ______ (hold) accountable for the failed merger, and their advisors ______ (expect) to justify the flawed strategy.

Answer: is held; are expected.

17) Fill in the blanks using two appropriate connecting words: I wanted to attend the seminar, ______ I was feeling unwell; ______, I stayed at home and watched the recorded lecture.

Answer: but; therefore.

18) Translate into English: প্রজেক্টের সময়সীমা কম থাকায় দলটি অতিরিক্ত সময় কাজ করতে বাধ্য হয়েছিল।

উত্তর: As the deadline of the project was short, the team was compelled to work overtime.

19) Rewrite using inversion: We rarely see such an honest and dedicated officer these days.

Answer: Rarely do we see such an honest and dedicated officer these days.

20) Change into passive voice: The manager made all the staff work overtime to complete the project.

Answer: All the staff were made to work overtime by the manager to complete the project.

সাধারণ জ্ঞান:

21) এশিয়ার দীর্ঘতম নদী কোনটি? এর দৈর্ঘ্য কত?

উত্তর: ইয়াংসি (চ্যাং জিয়াং), চীন; দৈর্ঘ্য প্রায় ৬,৩০০ কিলোমিটার।

22) উত্তর আমেরিকা ও দক্ষিণ আমেরিকাকে বিচ্ছিন্ন করেছে কোন প্রণালী?

উত্তর: পানামা খাল।

23) বিশ্বের বৃহত্তম ব্যাংকের নাম কী?

উত্তর: ইন্ডাস্ট্রিয়াল অ্যান্ড কমার্শিয়াল ব্যাংক অব চায়না (ICBC) — মোট সম্পদের ভিত্তিতে।

24) কোন নগরী পৃথিবীর দুটি মহাদেশে অবস্থিত?

উত্তর: ইস্তাম্বুল (ইউরোপ ও এশিয়া)।

25) সর্বপ্রথম ভ্যাকসিন কত সালে এবং কে আবিষ্কার করেন?

উত্তর: ১৭৯৬ সালে, এডওয়ার্ড জেনার (গুটিবসন্তের টিকা)।