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Understand centripetal and centrifugal forces, rotational and tangential speed, axis, rotation, and revolution in circular motion. Learn the formulas and concepts with examples.
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Circular Motion Things that Travel in a CIRCLE!!
Axis: A straight line around which circular motion takes place • Rotation: When an object turns about an “internal” axis (an axis located within the body of the object), also called spin • Revolution: when an object turns around an “external” axis (an axis not necessarily connected to the body)
Rotational Speed (Angular Speed): number of rotations per unit of time It is expressed in revolutions per minute RPM • Tangential Speed: is directly proportional to rotational speed and the distance from the axis (kinda like “regular” speed)
Centripetal Force: any force that causes a body to move in a circular path or in part of a circular path, such as rounding a corner • The only force exerted on an object moving in a circular path is directed toward the center of circular motion
Centrifugal Force: name given to a outward-acting force, and it is useful only in a rotating system • It is different from a real force in that there is no interaction (pair of forces), there is no mass out there pulling on it • There is no reaction counterpart to the centrifugal force that is felt, therefore it is not a real force
Fc (Centripetal Force) ac (centripetal acceleration) What do you think these mean? Basically that the object is moving with circular motion
New formulas Quantity Unit Formula Centripetal N Fc = mac Centripetal m/s2 ac= v2/r Force acceleration
Example A 0.25 kg mass is attached to a 1.00 m length of string. The mass is moving in a horizontal circle at a speed of 15.0 m/s. What is the centripetal force acting on the mass?