What is torque?
The turning effect of a force — force times the perpendicular distance from the pivot, measured in newton metres. Applying 20 N at 0.5 m from a bolt gives 10 N·m. The distance matters as much as the force, which is why a longer spanner loosens a stubborn bolt that a short one cannot: you are not stronger, you have more leverage.
Why does the angle matter?
Only the component of force perpendicular to the lever arm produces rotation, so torque is F × r × sin θ. Push straight along the spanner, at 0°, and you generate no torque at all — just a force trying to slide the tool off. Push at 90° and every newton counts. At 45° you lose about 30% of the effect, which is why awkward angles make jobs feel disproportionately hard.
What is the difference between torque and power?
Torque is turning force; power is the rate of doing work, equal to torque times rotational speed. An engine can produce high torque at low revs — good for pulling away and towing — while peak power arrives higher up the rev range. It is why a tractor and a sports car have very different characters despite comparable power figures.
Why are bolts tightened to a specified torque?
Because torque is a proxy for the clamping force stretching the bolt. Too little and the joint loosens under vibration; too much and the bolt yields or the thread strips. Published torque specs assume a particular lubrication state — a lubricated thread reaches the same tension at noticeably lower torque than a dry one, so applying a dry spec to an oiled bolt over-tightens it.
How do I convert between torque units?
One newton metre is about 0.738 pound-feet, and one pound-foot is 1.356 N·m. Also common is the kilogram-force metre, roughly 9.81 N·m. Watch for pound-feet versus foot-pounds — dimensionally identical and often used interchangeably, though strictly foot-pounds denotes energy and pound-feet denotes torque. Both appear on tools, so read the tool rather than the convention.
What is the relationship between torque and angular acceleration?
Torque equals moment of inertia times angular acceleration — the rotational counterpart of F = ma. Moment of inertia depends not just on mass but on how far that mass sits from the axis, which is why a flywheel with its mass at the rim resists speed changes far more than a solid disc of the same weight.