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Physics Daily Intro 1/3/18. Welcome Back!! Some changes to class structure “Board Work” Discussion Days New class website!!. Energy, Work, & Simple Machines. Physics: Chapter 10. Energy & Work 10.1. What is Energy, Work?. What are some things that uses energy or requires work ?
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Physics Daily Intro 1/3/18 • Welcome Back!! • Some changes to class structure • “Board Work” • Discussion Days • New class website!!
Energy, Work, & Simple Machines Physics: Chapter 10
What is Energy, Work? • What are some things that uses energy or requires work? • In physics, we need to be specific in how we refer to these ideas
Energy • Energy is a property of an object that describes the object’s ability to change its environment or in itself • Types of energy include chemical, thermal, andmotion
Energy & Motion Some object of mass is moving with a velocity when a force is applied, accelerating the object to a velocity of over a distance
Let’s Do Some Math • A kinematic equation that uses most of the knowns: • Need to find acceleration (we have force and mass) means that • Plug that into the kinematic equation • Do some algebra
Cool, but what does it mean? * This is the energy in the system * Kinetic Energy: * Property of the system, like momentum * This is the work done to the system * Work:
Joules Energy, and by extension work, are both measured using Joules Joule (J) =
Example Problem: Calculating Work • A 105 gram hockey puck is sliding across the ice. A player exerts a constant 4.5 N force over a distance of 0.15 meters. How much work does the player do on the puck? What is the change in the puck’s energy?
Big Points • Kinetic Energy is calculated • It is a property of the system • Work is calculated • It is a property of the environment • Work-Energy Theorem: • Work is equal to the change in kinetic energy • Work and energy are related
Minor Points • Energy is transferred between environment and system • If environment is doing work, +W • If system is doing work, W • Work formula () works only with constant force applied in the direction of motion • If a force is perpendicular to motion, work is 0
Practice Problems: Page 227 • Complete practice problems 1 – 5 on page 227 over calculating work and change in kinetic energy