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How It Works
Torque (τ = F · d) is the rotational equivalent of force. It measures how effectively a force causes rotation about a pivot. A longer lever arm or a larger force produces more torque. The same equation can be rearranged to solve for force or distance.
Example Problem
A mechanic applies 80 N of force at the end of a 0.3 m wrench. What torque is produced?
- τ = 80 × 0.3 = 24 N·m
If the bolt requires 24 N·m, this force is just enough to turn it.
Frequently Asked Questions
What is the difference between torque and moment?
In practice they are the same (force times distance). Engineers often use “torque” for rotation about a shaft and “moment” for bending in beams, but the math is identical.
Why does a longer wrench make bolts easier to turn?
A longer wrench increases the lever arm (d), so less force is needed to achieve the same torque. This is the mechanical advantage of a lever.
What units are used for torque?
SI: newton-meter (N·m). Imperial: foot-pound (ft·lbf). Automotive specs often use both. Note that N·m (torque) and J (energy) have the same dimensions but measure different things.
Related Calculators
- Moment Calculator — the same concept applied to structural analysis.
- Force Equation Calculator — find the force component.
- Power Calculator — power from torque and angular velocity.
- Horsepower Calculator — convert between torque, RPM, and horsepower.
- Torque Converter — convert torque units between N-m, ft-lb, and in-lb.
Reference: Lindeburg, Michael R. 1992. Engineer In Training Reference Manual. Professional Publication, Inc. 8th Edition.