forceVersion en ligne force is a vector quantity that measures the intensity of the exchange of momentum between two particles or particle systems par rafael alberto parra galindo 1 kinds of forces 2 definition kinds of forces frictional force gravity thrust force force of attraction repulsion force The force is attractive if they are of opposite sign The force is repulsive if the charges are of equal sign Gravity is one of the four fundamental interactions observed in nature the normal force F_n \, (or N) is defined as the force exerted on a body surface resting on it The thrust force is a force that occurs when a body is immersed in a fluid