The table exerts a normal force N on the box. Example of a box on a table shown in the figure below. Normal ForceThe normal force is the force exerted by an object onto another object when in contact.Two forces of equal magnitude and opposite direction acts on each of the magnets in the figure below. Magnetic ForceIt is the force exerted on a magnet that is located in a magnetic field.Two forces of equal magnitudes and opposite direction act on two charges of different signs in the figure below. Electric Force on a ChargeIt is the force exerted on a charge that is located in an electric field.It is also called the weight of an object. This force is due to the gravitational field of the earth. Gravitational ForceIt is the force exerted by the earth on any object with a mass.A person that is pushing a box, is applying an external force on the box. Applied External ForceAny force applied to an object externally by another object, human or animal.Ĭlassification of Forces A force can be put in one of the two classes: Forces with contact and forces at a distance.Ī) Examples of forces with contact 1) The force exerted by person to push a trolleyĢ) The force (tension) exerted by a string on a suspended objectģ) The force exerted by the ground on a table in a room (normal force)ī) Examples of Forces at a distance (also called field forces) 1) The force exerted by a planet (Earth for example) on any object with a mass.Ģ) The force exerted by an magnet on another magnet.ģ) The electric force exerted by an electric charge on another electric charge. Therefore, the newton (N) is the magnitude of the force applied to an object of a mass of 1 Kg in order to acquire an acceleration of 1 m/s 2. Action and reaction forces acts on different objects and have equal magnitudes.Ī force is represented mathematically by a vector because both magnitude and direction are important to describe the force. Forces are used to push or pull stationary objects, to stop moving objects, to change direction of moving objects.įorces always exist in pairs: a force of action and a force of reaction (third law of Newton).
This interaction may be at a distance or through contact. The weight of an object is the force of attraction that the earth exerts on this object. You need to exert a force to pull a box on the floor. A force is a vector quantity: its has a magnitude and a direction. What are Forces in Physics? A force describes, quantitatively, the interaction between two objects.
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