# lab 3 - Experiment 3Rotations Abstract: In this experiment,...

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Experiment 3—Rotations Abstract: In this experiment, an apparatus with a rotatable vertical shaft, a spring horizontal to the shaft, and a plumb bob attached to the spring and hanging from a bar perpendicular to the shaft were used to determine centripetal force when the shaft was rotated. By recording the average time of rotation when the centripetal force was equal to that of the opposite force that would counteract the spring, we were able to determine the centripetal force and compare it to the gravitational pull on a graph. Questions: 1.a. Uniform circular motion is the motion of an object moving at a constant speed around a circle. b. An object that is in uniform circular motion is accelerating because since it is not traveling in a straight line, but in a circular motion, the velocity is constantly changing. When velocity is changing, the acceleration is not constant. c. Centripetal acceleration is caused by the force that is always directed toward the center of a circle when an object is moving in a circle. Its magnitude is equal to (v^2)/r, where v is velocity (which is constantly changing direction as it moves around the circle) and r is the radius of the circle. 2. Begin with a car moving at 10meters/second around a track with a radius of 50 meters. The equation for acceleration is (v^2)/r, so the magnitude of this car’s acceleration would be 2m/s^2. If the speed was doubled to 20m/s and the radius remained 50m, acceleration would be 8m/s^2. If the radius was cut in half to 25m and the velocity remained 10m/s, the acceleration would only

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be 4m/s^2. Therefore, doubling the speed has a greater effect on the magnitude of acceleration than does halving the radius. 3. a. Centripetal force is the net force directed toward the center of a circle when an object is
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## This note was uploaded on 11/17/2011 for the course PHYSIC 131 taught by Professor Staff during the Fall '10 term at UMass (Amherst).

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lab 3 - Experiment 3Rotations Abstract: In this experiment,...

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