As you go on studying physics, you will realize that a large part of it is devoted to the study of 'Motion', its causative agents, and the anatomy of motion. All kinds of motion are the result of the energy changes caused by the presence of unbalanced forces in nature. In the study of motion, one essential concept, which needs to be grasped is 'acceleration' of an object, caused by a force. Definition The best way to understand any physics concept is to relate it as much as possible, with experience. You may not know what is acceleration but you have already felt it. When the car you are sitting in speeds up, what you feel is acceleration, caused by the change in speed of the car. In technical terms, it is defined to be the rate of change of velocity with time. Velocity is the rate of change of displacement with time, in a specific direction. Acceleration is not just a change in the magnitude of velocity (speed), but it also indicates a change in the direction of displacement of any object. Force causes a change in velocity and causes an object to accelerate. The unit of linear acceleration is meters/sec². Formula Acceleration (a) = Force (F)/Mass (m) Angular Acceleration The acceleration caused in a body may not always be linear. What objects that rotate around a center feel is angular acceleration. It is defined in physical terms as the rate of change of angular velocity of any object with time. The formula for it is as follows: Angular Acceleration (α) = dω/dt = τ / I where ω is angular velocity, τ is the torque (rotational force) acting on an object, and I is its moment of inertia. Centripetal Acceleration When you tie an object on a string and rotate it in a circular fashion, it feels a centripetal force directed towards the center. The object feels a centripetal acceleration directed towards the center of circular motion. The formula is as follows: Centripetal Acceleration (a) = v² / r where v is the linear or tangential velocity of the rotating object and r is the linear distance of the object from the center of rotation. Acceleration Due to Gravity Although, gravity is now understood to be a manifestation of the curvature of space time, caused by mass, it can still be approximately described by Newton's law of gravitation. The force of gravity exerted on an object, accelerates it. Newton's law of gravitation is stated as follows: F = Mass (m) x Acceleration Due to Gravity (g) Since Earth is not a perfect sphere, the mass exerted by it is not exactly same on all points of its surface. The value of acceleration due to gravity, provided by the above equation varies from the equator to the poles. It is greater at the poles and has the lowest value at the equator, as Earth is actually shaped like a flattened sphere or oblate spheroid. Its average value due to gravity on Earth is 9.80665 m/s².