Angular Acceleration vs Centripetal Acceleration
Angular acceleration and centripetal acceleration are two phenomena encountered in dynamics of bodies. While these two may seem much alike each other, they truly are two very different events. These effects can be observed on bodies moving on circular paths, namely circular motion for centripetal acceleration and angular motion for angular acceleration. All accelerations, including angular acceleration and centripetal acceleration occur due to forces.
Angular acceleration
Angular acceleration is an event discussed in the angular motion. Motions like blades of a fan, or a wheel running have angular motion. For the angular motion, an angle drawn radially is used. One side of this angle moves with the object as the other remains still with respect to earth. The angle is known as angular displacement. The rate of change of angular displacement is known as angular velocity and rate of change of angular velocity is known as the angular acceleration. It has the units of radians per second per second (rad/s^{2}). The terms angular displacement, angular velocity and angular acceleration correspond to their partners in linear motion displacement, velocity and acceleration respectively. The angular acceleration is a vector. It has the direction of the axis of the system. The corkscrew law can be used to determine the direction. Imagine a right handed corkscrew turning in the direction as same as the angular motion, the direction the corkscrew “tries” to go is the direction of the angular acceleration.
Centripetal acceleration
Centripetal acceleration occurs due to the centripetal force. Centripetal force is the force which keeps the objects in a circular or any curved path. The centripetal force always acts on the direction of the immediate center of the motion. Centripetal acceleration is the acceleration, which occurs due to the centripetal force. It obeys the Newton’s second law of motion in the form of centripetal force = centripetal acceleration x mass. The centripetal force necessary for keeping the moon on orbit around the earth is provided by the gravitational force between earth and moon. The centripetal force necessary for keeping a car from deviating from a turn is produced by the friction and the normal force from the surface acting on the vehicle. Since the centripetal acceleration is directed towards the center of motion, the object tries to come close to the center. A centrifugal force is necessary to balance this. Centripetal acceleration is measured in meters per seconds squared, which is s linear quantity.
Centripetal Acceleration vs Angular Acceleration 1. Both centripetal and angular acceleration are vectors. 2. Centripetal acceleration is measured in ms^{2}, while angular acceleration is measured in rads^{2}. 3. In a circular motion, the centripetal acceleration takes the direction towards the center, which varies over the circulation, but the angular acceleration takes the direction of the corkscrew law, which is a fixed direction. 4. Angular acceleration is an angular quantity, while the centripetal acceleration is a linear quantity. 5. For an object circulating with a fixed angular velocity the angular acceleration is zero, while the centripetal acceleration has a value of radius x angular velocity^{2}.

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