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Unformatted text preview: 1 Potential Energy of a Spring F applied kx The work done by the applied force is stored in the spring in 2 2 1 kx Area Work kx x 2 2 1 kx PE spring W force is stored in the spring in the form of potential energy: Textbook Page 233, Example 8-8, Spring Time A 1.70-kg block slides on a horizontal, frictionless surface until it encounters a spring with a spring constant of 955 N/m. The block comes to a momentary rest after compressing the spring a distance of 4.60 cm. Find the initial speed of the block. (Ignore air resistance and any energy lost when the block initially contacts the spring.) 2 2 1 kx PE spring Conservation of mechanical energy i i f f PE KE PE KE 2 2 2 2 2 1 2 1 2 1 2 1 i i f f kx mv kx mv Normal force (nonconservative) does no work . W nc = 0 v f = 0, x i = 0 v i = ? 2 2 2 2 ) )( / 955 ( ) 7 . 1 ( ) 046 . )( / 955 ( ) / )( 7 . 1 ( m s N v kg m m N s m kg i v f = 0, s m v i / 09 . 1 x f =- 0.046m, x i = 0 x f =- 0.046m, 2 Total mechanical energy S i 2 energ potentia nal Gravitatio T l ti 2 mechanical Total 2...
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