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**Unformatted text preview: **PHYSICS 231 INTRODUCTORY PHYSICS I Lecture 7 • Work (constant force) • Kinetic Energy • Work-Energy Theorem • Potential Energy of gravity • Conservation of Energy Last Lecture W = ρ Φ ( ρ ξ φ- ρ ξ ι 29 = Φ∆ξχοσθ KE = 1 2 μ ω 2 KE f- KE i = W net ∆ PE = mgh PE f + ΚΕ φ = ΠΕ ι + ΚΕ ι ∆ΚΕ = -∆ΠΕ Work and PE for nonconstant force F x x 1 x 2 ∆ x Work = = Area under curve = - ∆ PE F x D x ∆ W = F x D x Springs (Hooke’s Law) Proportional to displacement from equilibrium F = -κξ Potential Energy of Spring PE = 1 2 κξ 2 F app = - F spring = kx ∆ PE = Area under curve =(1/2)(base)(height) =(1/2)(F max )(x max ) =(1/2)(kx)(x) F max x Example 5.7a a) What is the spring constant? A 0.50-kg block rests on a horizontal, frictionless surface as in the figure; it is pressed against a light spring by a force of 16 N, with an initial compression of 2.0 cm. 800 N/m x Example 5.7b b) The block is released. To what height h does it rise when moving up the incline?...

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