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S E C T I O N 15 . 4 • Comparing Simple Harmonic Motion with Uniform Circular Motion 465 15.4 Comparing Simple Harmonic Motion with Uniform Circular Motion Some common devices in our everyday life exhibit a relationship between oscillatory Figure 15.14 is an overhead view of an experimental arrangement that shows this relationship. A ball is attached to the rim of a turntable of radius A, which is illumi- as the turntable rotates with constant angular speed, the shadow of the ball moves To find the new amplitude, we equate this total energy to Note that this is larger than the previous amplitude of A ! √ 2E k ! √ 2(1.15 , 10 " 2 J) 20.0 N/m ! 0.033 9 m E ! 1 2
kA
2 total energy to the kinetic energy when the cart is at the This is larger than the value found in part (a) as expected v max ! √ 2E m ! √ 2(1.15 , 10 " 2 J) 0.500 kg ! 0.214 m/s E ! 1 2
mv max 2 Figure 15.13 (a) The pistons of an automobile engine move in periodic motion along a single dimension. This photograph shows a cutaway view of two of these pistons. This motion is converted to circular motion of the crankshaft, at the lower right, and ultimately of the wheels of the automobile. (b) The back-and-forth motion of pistons (in the curved housing at the left) in an old- fashioned locomotive is converted to circular motion of the wheels. © Link / V isuals Unlimited Lamp Ball Q P A A Screen Turntable Shadow of ball Active Figure 15.14 An experimental setup for demonstrating the connection between simple harmonic motion and uniform circular motion. As the ball rotates on the turntable with constant angular speed, its shadow on the screen moves back and forth in simple harmonic motion. At the Active Figures link at http://www.pse6.com, you can adjust the frequency and radial position of the ball and see the resulting simple harmonic motion of the shadow. Courtesy of Ford Motor Company (a) (b) |