Rotationskraften

Rotationskraften, often translated as rotational force or torque, is a fundamental concept in physics that describes the tendency of a force to cause an object to rotate about an axis or pivot. It is the rotational analog of linear force. Just as force is the agent that causes linear acceleration, torque is the agent that causes angular acceleration.

The magnitude of torque is determined by three factors: the magnitude of the applied force, the distance from the pivot point to where the force is applied (known as the lever arm), and the angle between the force vector and the lever arm. Mathematically, torque (often denoted by the Greek letter tau, $\tau$) is calculated as the cross product of the position vector from the pivot to the point of force application and the force vector itself. In simpler terms, for a force applied perpendicular to the lever arm, torque is the product of the force and the lever arm length. The unit of torque in the International System of Units (SI) is the newton-meter (Nm).

Torque is a vector quantity, meaning it has both magnitude and direction. The direction of the torque vector is perpendicular to both the force and the lever arm, and its sense indicates the direction of rotation. A common convention is to use the right-hand rule to determine the direction of torque.

Understanding rotationskraften is crucial in many areas of physics and engineering, including the analysis of machines, the behavior of rotating machinery like engines and turbines, and the motion of celestial bodies. It explains why applying force further from a hinge makes an object easier to open or close, or why a longer wrench makes it easier to loosen a stubborn bolt.