Net Force (College Board AP® Physics 1: Algebra-Based)

Net forces

• The net force on a system is the vector sum of all forces exerted on the system

• This net force determines

  • whether the object or system will experience a change in its direction of motion

  • whether the object or system will experience a change in the speed of its motion

• The net force is sometimes called the resultant force

• An object or system cannot exert a net force on itself

• Forces can combine to produce

  • balanced forces

  • unbalanced forces

• When the configuration of the forces acting on a system is balanced then the system is in translational equilibrium and the net force exerted on the system is zero

• When the configuration of the forces acting on a system is unbalanced then the net force exerted on the system is not equal to zero

  • For example, imagine two people playing a game of tug-of-war, working against each other on opposite sides of the rope

  • If person A pulls with 80 N to the left and person B pulls with 100 N to the right, when the vectors of these forces are added together they do not cancel each other out completely

  • Since person B pulled with more force than person A the system will be unbalanced and the rope will experience a resultant force of 20 N to the right

Net force not equal to zero