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  1. 1. Lesson 1<br />How do machines help people work?<br />Using force in order to move an object a certain distance.<br />Work is measured in an unit called joule (J).<br />W= F X D<br />Multiply the force and distance to measure work.<br />
  2. 2. Work and Machines<br />Machine<br />Any device that helps people do work.<br />Simple Machines<br />Made of one or two parts.<br />Nail clippers and chopsticks.<br />Compound Machines<br />Cars, trucks, airplanes.<br />Has one or more simple machines among its parts.<br />
  3. 3. How machines help<br />They make it easier to work<br />A car jack and a crowbar are examples of machines that increase the amount of force to lift or move an object<br />Other machines change the distance over which force must be applied.<br />
  4. 4. Machines and Friction<br />Not all the energy you put into machine is used to do work because some energy is lost due to friction.<br />Friction is created when the moving parts of a machine rub together.<br />There are ways to reduce friction.<br />Using wheels and rollers.<br />Friction creates heat and slows down machine´s parts.<br />Coating the machine parts with grease , oil or wax.<br />