kraftmengden

Kraftmengden is a term used in Norwegian-language physics and engineering to describe the set or quantity of forces acting on a body or system. In common usage it is closely related to the net force, the resultant force that governs motion according to Newton's laws.

It includes all external forces such as gravity, contact forces (normal and friction), and any applied loads, as well as internal constraint forces within a structure. The Kraftmengden is the vector sum of these forces, F = Σ F_i, computed in a chosen coordinate system and direction convention. The resulting vector determines the acceleration through F = m a.

More formally, for a particle of mass m, the Kraftmengden F(t) equals the time rate of change of momentum p, d p / d t = F(t). The impulse over a time interval Δt equals Δp. In systems with rotation or multiple components, the concept extends to the vector sum of forces acting on each part, consistently with the chosen reference frame.

Example: a block on a frictional incline experiences gravity, a normal force, and kinetic friction. The net force along the incline is F_net = m g sin θ − μ_k m g cos θ, yielding an acceleration a = F_net / m, with sign determined by the chosen axis.

Applications and distinctions: in statics, the Kraftmengden is zero for a body in equilibrium. In dynamics, it drives motion and deformation. Engineers use the concept in static and dynamic analysis, design, and simulations to assess safety and performance, and it underpins related ideas such as impulse and momentum.