Types of forces

     There are two many types forces. They divided into five groups, all of them have the gravity in common. The five types of forces are the Gravity force, the Normal force, the Friction force, the Air resistance force and the Tension force. Firstly, the Gravity force is the force which all the objects act downward in the center of the earth. It's equal with the weight of the objects. Also, Normal force is the force which acts in an object which this object is in contact with a second object. For example, a book is stable on the table. The table acts in the book the same force which the book acts on the table. Moreover, the friction force is created when an object is moving on a surface. The friction force is giving by the formula: f=N*m, which N is the Normal force which is equal with the weight of the object and m is a constant. Also, the air resistance force is created when an object like an airplane is moving in the air. Finally, the tension force is the force between the object and a rope. The object it is connected with the rope and the tension is the rope is equal with the weight of the object. These five groups of forces are based on the gravity.