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Uniform circular motion




Newton's first law

Notice the motion of the ball after the string is cut.


A wooden ball is attached to the rim of a spinning wheel. The ball is held in place by a string. After the spring is cut, the ball flies upward in a straight line tangent to the wheel, initially with the same speed it had when in uniform circular motion.
In the camera's frame of reference, the ball constantly accelerates around in a circle due to the centripetal force pulling it inwards (Newton's second law). When the string is cut, the acceleration stops, and the ball flies away in a straight tangential line (Newton's first law).


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