Forces. Net force

Force, Net Force

In physic, force is a push or a pull that act over an object. Force can be capable of changing the velocity of the object.

Forces are measured in “Newtons” or “N”, in honor of Sir Isaac Newton. According to Mr. Newton, an object will only accelerate if there is “unbalanced force” acting upon it. 

Force has size and direction. Size refers to the magnitude or value of the force and direction refers to the direction in which the force is applied.

Sometimes over the same object acts different forcers. The combination of all forces acting on an object is called net force.

When the forces acting over an object have the same direction, the value of the net force wills the result of addition of all the forces; and the direction will be the same of the forces acting over the object. Let see an example.

When the forces acting over an object have different directions, the value of the net force wills the result of the subtraction of all the forces acting over the object. The direction will be the same direction of the force with the major value. Let see an example.

We are in presence of Balanced Forces, when the net force acting over an object is zero. The velocity is constant.

We are in presence of Unbalanced Force, when the net force acting over an object is different to zero. Unbalanced forces acting on an object changes its speed and/or direction of motion.

Free-body diagrams for four situations are shown below. For each situation, determine the net force acting upon the object. 

Represents and calculate the net force in each one of the following situations.

1. A boy pulls a wagon with a force of 6 N east as another boy pushes it with a force of 4 N east.

2. Mr. Smith and his wife (Mrs. Smith) were trying to move their new chair. Mr. Smith pulls with a force of 30 N while Mrs. Smith pushes with a force of 25 N in the same direction.

3. The Colts team is playing tug of war. Mrs. Larson’s homeroom pulls with a force of 50 N. Ms. Mitko’s homeroom pulls with a force of 45 N in the opposite direction. What is the net force? And who won?