Unit of Torque: Definition, SI and Other Units

Introduction

The moment of force or torque is the force delivered to an object to cause it to rotate. When an item moves over distances greater than its own size, it is referred to as a point object. Kinematics is used to explain the motion of these point-sized objects in one, two, and three dimensions, and some work is necessary to modify the configuration and motion of these objects.

What is Torque?

The rotating equivalent of linear force is defined as torque. The axis of rotation is the point at which the item rotates.

A point object is one whose magnitude is less than the movement of an item over a defined distance. Kinematics is used to explain the motion of point objects in one, two, and three dimensions. Point objects are often composed of very large particles. Newton’s laws of motion describe the rotating behaviour of these limitless particles.

Formula

T = F × r × sinθ

T is for torque, while F is for linear force.

r = the distance measured from the rotation axis to the point at which linear force is applied.

θ = the angle between F and r

In this formula, sinθ has no units. ‘r’ has units of metres (m), and ‘F’ happens to have units of Newtons (N). Combining these, one can see that a unit of this force is a Newton-metre (Nm).

Importance of Torque

• Torque illustrates the notion of rigid body rotational motion.
• The idea of torque may identify the direction and intent of a force applied to a body.
• It also controls the clockwise and anti-clockwise movement of the body.
• When a body rotates, torque determines the angular acceleration.

What is the SI Unit of Torque?

Torque is represented by the Greek letter tau: τ in calculations. M represents the moment of force when it is referred to as such. Torque is defined as the dot product of force and position vector. The SI units of force and distance are newtons (N) and metres (M). As a result, the International System of Measurement (SI) unit for torque is newton-metre or Nm.

Although the Newton metre is equivalent to joules, the SI unit for energy or work, torque is only measured in newton-metres.

Torque is measured in imperial terms as pound-force-feet (lb-ft), which can be shortened to pound-foot. The dimension of torque is [M¹L²T^-2].

Other Units of Torque

Torque can also be quantified in imperial quantities such as inch-pounds-force, pound-force-feet (lbf⋅ft), ounce-force-inches (ozf⋅in), and foot-pounds-force (fpf). Some of the other non-SI units of torque include metre-kilograms-force.

Real-life Applications of Torque

• Old Telephone- We used to rotate the numerals on the dial in either a clockwise or counterclockwise orientation. Torque is the rotational force applied by our fingers on the dial.
• Ferris Wheel- The Ferris wheel’s wheel is revolving around its axis, and the torque drives this wheel to rotate.
• Lock-Key- The lock opens when you twist the key within the lock. The twisting motion of the key is caused by the torque.
• Gyroscopes- Gyroscopes have a flywheel, which is a wheel-like disc mounted on an axle. Torque causes a spin in the flywheel axis, which is perpendicular to the rotor axis.
• Seesaws- Seesaws demonstrate the operation of the torque’s two most important components, force and moment arm. The balancing point is the seesaw’s pivot point. A heavyweight can minimise torque by sitting closer to the point, and vice versa.
• Hinged doors- The torque is what causes a hinged door to open and close when the hinge is the pivot point. If you put force near the door’s hinges, it will not open since there is insufficient torque force.

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