draaimoment

Draaimoment, in Dutch often referred to as torque or moment of force, is the rotational effect that a force can produce about a specific axis or pivot. It describes the tendency of a force to cause a body to rotate. The unit is the newton-meter (N·m). The concept is geometric as well as dynamic: the magnitude and direction depend on how far the force is applied from the axis (the lever arm) and on the angle between the force and the lever arm.

Mathematically, the draaimoment τ is the cross product of the position vector r (from the axis to the point of application) and the force vector F: τ = r × F. Its magnitude is τ = r F sin θ, where θ is the angle between r and F. The direction of τ is given by the right-hand rule, indicating the axis about which rotation tends to occur. In rotational dynamics, τ is related to angular acceleration α by τ = I α for a rigid body with moment of inertia I about the chosen axis.

Torque also connects to power and work: the instantaneous power delivered by the torque is P = τ ω, where ω is the angular velocity. The work done by the torque over a rotation by angle θ (in radians) is W = ∫ τ dθ; for constant τ, W = τ θ.

Common examples include turning a bolt with a wrench or the torque produced by an engine. Draaimoment is distinct from energy; it is a measure of rotational effect, while work and energy quantify the amount of rotation and energy transfer.