Net force

Science

Definition

Net force is the vector sum of all forces acting on an object. When the net force is zero, the object is in equilibrium (at rest or moving at constant velocity). When the net force is nonzero, the object accelerates in the direction of the net force according to Newton's second law.

Examples

  • A book on a table with gravity balanced by the normal force, resulting in zero net force
  • A car accelerating because the engine force exceeds friction and drag
  • Tug-of-war where the stronger team creates a net force in their direction
Key Fact

ΣF = ma (Newton's second law).

Related Terms

Newton's three laws Free-body diagrams Acceleration Friction

Study This Concept

Practice net force with free review games in these units:

AP Physics 1 Unit 2: Forces and Newton's Laws