Ch 13 part 2 Simple Machines Pages 426-431 http://dai.ly/x3cvmov http://www.dailymotion.com/video/x3cvmov ` A. Machines and work Work is done when force causes an object to move Machine= device that changes the direction or amount of force needed to do work 1. 2. ◦ 3. DO NOT reduce work= just make it easier to do the work The amount of force decreases BUT the force must be applied over a greater distance B. Simple Machine #1 Pulley https://youtu.be/aMx7nIIH9ik?t=47s 1. Pulley= consists of a rope or cable that runs through a grooved wheel 2. Simple pulley makes work easier by changing the direction of force needed to do work 3. Block and tackle= system of pulleys that make it easier to lift very heavy objects Block= pulley and the tackle is the rope through the pulleys C. Simple machines #2 Wheel and Axle https://youtu.be/P7xu9O0miEc?t=47s Wheel and axle= made of a circular object and a shaft 1. ◦ ◦ Reduces the amount of force needed to do work Door knob, steering wheel, Stop and Think What is a machine? 1. ◦ A device that changes the direction or the amount of force needed to do work How are a pulley and a wheel and axle alike and different? 2. ◦ Both have wheels ◦ A pulley has a rope & it changes the direction of the force ◦ A wheel& axle has a shaft & it reduces the amount of force needed to do work When a wheel and axle as well as a pulley make it easier to raise a bucket of water from a well, has the work changed? 3. ◦ The amount of work has not changed b/c the amount of work has stayed the same- the machine made it easier to do the work D. Simple machine #3 Lever https://youtu.be/OdM2jWg2uEE?t=46s Lever= type of simple machine in which a stiff bar rotates around a fixed point called the fulcrum 1. ◦ ◦ A see-saw is a fulcrum that changes the amount of force needed to move an object Further away the fulcrum is from the person the easier the lever is to use E. Simple Machine #4 Inclined Plane https://youtu.be/E_ErI0QjNos?t=49s Inclined plane= simple machine consists of a flat surface with one end higher than the other 1. ◦ Doorstops & axes are inclined planes Screw= smooth metal rod with tin inclined planes wrapped around it 2. ◦ Archimedes invented the screw in ancient Egypt (3rd century B.C) to move water from the ground 3. Wedge= inclined plane used to separate objects Stop and Think What common playground equipment is a lever? Which is an inclined plane? 1. ◦ ◦ See-saw (teeter totter) Slide How is the movement of rolling a weight up an inclined plane different from climbing stairs? 2. ◦ Climbing stairs requires more force What kind of simple machine is a bottle opener? 3. ◦ A lever F. Complex Machines https://youtu.be/k_aTRL2Ircw Complex machine uses 2 or more simple machines 2. Many use electricity, magnetism, gravity, burning fuel, or human force to use 1. Stop and Think What is a complex machine? 1. ◦ Machine that uses 2 or more simple machines How are the pedals of the go cart similar to the rudder of a sailboat? 2. ◦ Both use levers What parts of a complex machine work together to make the complex machine operate? 3. ◦ All of the simple machines work together to make the complex machine operate!