**Unformatted text preview: **ith a mass m located a distance x meJured along II the incline. Take the zero of potential eJ1ergy at the bottom of the incline. . Problem
9. A 1.50-kg brick measures 20.0 cmx8.00 cmx 5.50 em. Taking the zero of potential energy when the hrick lies on its broadest face, what is the potential energy (a) when the brick is standing on end and (b) when it is balanced on its 8-em edge, with its center directly above that edge? Note: You 'II I Ii :{(. CHAPTER 8 125 i~ treat
;~tion the brick as though all its mass is ncentrated at its center. Solution
From Equation 8-4, U = ~kX2 l(320 Njm)x (0.18 01)2 5.18 J is the maximum potential energy of the spring whose stretch.is not greater than 18 em. = = ><center of the brick is a distance D.y = 10 cm ~ em = 7.25 em above the zero of potential energy ~ition (a), and D.y = h/(20 cm)2 + (5.5 cm)2 5:cm 10.4 em -2.75 em 7.62 cm in position (~ee sketch; the center is midway along the .. nal of the face of the brick). From Equation 8-3, a,vitational potential energy is Ua mg D....

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