acceleration

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Rate of change of the velocity of a moving body. For example, an object falling towards the ground covers more distance in each successive time interval. Therefore, its velocity is changing with time and the object is accelerating. It is usually measured in metres per second per second (m s^-2) or feet per second per second (ft s^-2). Acceleration = change in velocity/time taken. Because velocity is a vector quantity (possessing both magnitude and direction), a body travelling at constant speed may be said to be accelerating if its direction of motion changes. According to Newton's second law of motion, a body will accelerate only if it is acted upon by an unbalanced, or resultant, force. Acceleration of free fall is the acceleration of a body falling freely under the influence of the Earth's gravitational field; it varies slightly at different latitudes and altitudes. The value adopted internationally for gravitational acceleration is 9.806 m s^-2/32.174 ft s^-2.

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