Travail effectué par plusieurs forces

The first method calculates work done by each force individually, then sums these values algebraically to find total work. The second method finds the net force through vector summation of all forces, then calculates work using this resultant. Both methods yield identical results and account for how forces at different angles contribute to displacement.

Forces perpendicular to an object's displacement do not cause motion in the direction of travel. Since work equals force component times displacement in the direction of motion, perpendicular forces have no component along the displacement direction, resulting in zero work contribution regardless of their magnitude.

Opposite forces acting on an object's center of mass contribute different positive and negative work values. Through algebraic summation, the overall work becomes positive or negative depending on which force has greater magnitude. The net force direction relative to displacement determines whether total work is positive, negative, or zero.

The pulling force component along the direction of motion and the frictional force both contribute to total work. The vertical component of the pulling force and the normal force are perpendicular to displacement, so they contribute zero work. Only forces aligned with or opposing the displacement direction affect the total work calculation.

The net force method requires calculating the vector sum of all forces first, including perpendicular components, before determining work. The individual force method calculates work for each force separately and can ignore perpendicular forces immediately. Despite this procedural difference, both approaches yield the same total work value when applied correctly.

Force direction determines whether work is positive or negative. Forces aligned with displacement produce positive work, while forces opposing displacement produce negative work. The angle between each force and displacement vector is critical; only the component of force parallel to displacement contributes to work calculations.

Yes, the net force method works for forces at any angle. First, resolve all forces into components and sum them vectorially to find the net force. Then calculate work using the net force magnitude and its angle relative to displacement. This method handles complex multi-force scenarios systematically.