subject: Force explained [print this page] The body uses muscle forces to stand upright against another force called gravity (external force). Gravity is defined as the force of attraction between two masses and always acts in a downward direction towards the earth's centre. Taking advantage of the earth's gravitational pull allows individuals to interact with the surrounding environment. However, take a look around a busy supermarket and you will notice that there are many individuals losing the fight against gravity (kyphotic posture).
