A force is a push or a pull. Forces can make objects move or alter their shape. Some forces are easy to recognise - you may pull on a door to open it or push it closed behind you. We constantly use forces to move ourselves around and to move other objects. Some forces, however, are less easy to understand. If you let go of a bag it falls to the floor. The pull of the Earth on an object is called the force of gravity. Two magnets attract one another if opposite poles are brought together. Magnetic forces are acting here. Electric forces can cause attraction between a plastic comb and your hair.
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