Lecture10

# Force f1 is horizontal with 60 magnitude 20 n force

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Unformatted text preview: is angled upward by 60º 2.0 to the floor and has a magnitude of 4.0 N. The speed 4.0 v of the box at a certain instant is 3.0 m/s. 3.0 a) What is the power due to each force acting on the box? Is the net power changing at that on the box? Is the net power changing at that instant? instant? • Potential Energy and Conservation of Energy • Conservative Forces • Gravitational and Elastic Potential Energy • Conservation of (Mechanical) Energy • Potential Energy Curve • External and Internal Forces b) If the magnitude F2 is, instead, 6.0 N, what is 6.0 now the net power, and is it changing? th it Lecture 9 Andrei Sirenko, NJIT 21 Lecture 9 Work and Potential Energy Andrei Sirenko, NJIT 22 Path Path Independence of Conservative Forces Potential Energy General Form: • The work done by a conservative force on a particle moving between two points does moving between two points does not depend on the path taken by the particle. Gravitational Potential Energy • The net work done by a conservative force on a particle moving around every closed path is zero. Elastic Potential Energy Lecture 9 Andrei Sirenko, NJIT 23 Lecture 9 Andrei Sirenko, NJIT 24 Conservation of Mechanical Energy Path Independence of Conservative Forces Mechanical Energy Sample Problem 8-1: A 2.0 kg block slides along a frictionless track from a to point b. The block travels through total distance of 2.0 m, block travels through a total distance of 2.0 m, and a net vertical distance of 0.8 m. How much work is done on the block by the gravitational force? Conservation of Mechanical Energy In an isolated system where only conservative forces cause energy changes, the kinetic gy and potential energy can change, but their sum, the mechanical energy Emec of the system, cannot change. Lecture 9 Andrei Sirenko, NJIT 25 Lecture 9 Andrei Sirenko, NJIT Kinetic Energy: Kinetic Energy: Potential Energy: 26 Potential Energy: • Gravitation: • Gravitation: • Elastic (due to spring force): • Elastic (due to spring force): 1 1 mg Lecture 9 y U K U Conservation of Mechanical Energy 2 Andrei Sirenko, NJIT K=0 27 K U=0 2 Conservation of Mechanical Energy Lecture 9 Andrei Sirenko, NJIT 28 QZ#10 Name, ID#, Section # ID#, Section Thermal Energy/Friction 4 days SF Conservation of Energy NYC • The total energy of a system total energy of system can change...
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## This document was uploaded on 03/31/2014 for the course PHYS 105 at NJIT.

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