Q1. Torque: What are you actually measuring when you say “torque”?
Torque has units of N·m and tells you the twisting demand around a shaft or fastener axis. In machines, it is the “twist load” that creates torsional stress or joint slip risk. The design relevance is whether the part can carry that twist without yielding, cracking, or loosening.
Q2. How is torque different from force?
Force is a push or pull. Torque is the force that a force produces about an axis when it acts with a lever arm. The same force can create very different torques depending on the perpendicular distance to the axis.
Q3. Why does the lever arm length change the torque so much?
Torque grows with the perpendicular distance to the axis because that distance creates a rotational tendency. That is why a longer wrench feels easier for the same tightening goal. In design terms, geometry can amplify or reduce the moment a component “feels.”
Q4. How do you compute torque from a simple setup?
You multiply the applied force by the perpendicular lever arm distance.
Micro example: if you apply 50 N at a 0.2 m radius, the torque is 10 N·m.
The interview-safe detail is “perpendicular distance,” not the visible length.
Q5. Why does a gearbox increase torque but reduce speed?
A gearbox trades rotational speed for turning capacity. Ignoring losses, power stays about the same, so raising torque usually means lowering RPM. In the real world, efficiency losses reduce the delivered output.
Q6. Torque vs power: how should you explain the difference quickly?
Torque tells you how strongly the system can twist. Power tells you how fast it can deliver energy. You can have high torque at low speed or lower torque at high speed and still deliver similar power.
Q7. How do engineers measure torque in practice?
You either measure shaft strain linked to torsion or infer torque from force and geometry in a controlled setup. In testing, instrumentation is preferred because it reports what the shaft actually carries. In assembly, tools control the applied twisting input, but the clamp load still depends on the friction scatter.
Q8. Torque wrench: what does the “click” mean, and what should you do next?
The click means the tool has reached its set torque and is signaling you to stop applying more turning moment. Release and reset your hand position rather than “pulling through” the click. This matters because extra motion after the click can overshoot torque and increase scatter.
Q9. What does RPM mean in rotating equipment?
RPM is revolutions per minute, a direct measure of rotational speed. It is not a force, and it is not a torque.
RPM matters because it drives power, heating, vibration behavior, and how many fatigue cycles a rotating part accumulates over time.
Q10. How do you connect torque, RPM, and power in a way an interviewer trusts?
Power equals torque multiplied by angular speed. A practical conversion is:
ower (kW) = Torque (N·m) × RPM / 9550.
Worked example: Suppose a motor delivers 60 N·m at 1500 RPM.
Power (kW) = 60 × 1500 / 9550 ≈ 9.42 kW.
If the same system runs at higher RPM with lower torque, power can stay similar, so speed and torque must be discussed together.
Torque–RPM–Power Quick Conversion Card
What you have
What you want
Quick relation (common units)
Torque + RPM
Power
Power (kW) = Torque (N·m) × RPM / 9550
Power + RPM
Torque
Torque (N·m) = Power (kW) × 9550 / RPM
Power + Torque
RPM
RPM = Power (kW) × 9550 / Torque (N·m)
SI reminder
Units
1 kW = 1000 W, torque in N·m, RPM in rev/min
