Simple Machines V 205 07 Simple Machines Devices

Simple Machines V 205. 07

Simple Machines � Devices such as levers, ramps, and pulleys that make our work easier. � They allow us to apply effort at one place to do work at another point and/or to change the direction of a force.

Simple Machines � One way is to magnify an effort force so that a smaller effort can be applied over a longer distance thus moving a large load a small distance. � Examples: �a crowbar being used to dislodge a boulder, �a nutcracker being used to crack a nut, �or a block tackle pulley system being used to lift a large weight. Source: http: //www. lakelandschools. org/EDTECH/Machines/Rube. Main. jpg

Simple Machines � The mechanical advantage of a machine is the ratio of the load force to the effort force. � The crowbar, nutcracker, and block and tackle pulley system have a mechanical advantage greater than one. � Other machines have a mechanical advantage less than one allowing magnification of the distance and speed of a movement. � An example of this might be a fishing rod or baseball bat.

Simple Machines � Inclined plane -- a sloping surface, such as a ramp. �An inclined plane can be used to alter the effort and distance involved in doing work, such as lifting loads. �The trade-off is that an object must be moved a longer distance than if it was lifted straight up, but less force is Source: http: //www. sirinet. net/~jgjohnso/inclineplanecolored. jpg needed. �Examples: staircase, ramp, and bottom of a bath tub

Simple Machines � Wedge -- two inclined planes joined back to back. � Wedges are used to split things. � Examples: Axe Zipper Knife

Simple Machines � Screw -- an inclined plane wrapped around a shaft or cylinder. �This inclined plane allows the screw to move itself or to move an object or material surrounding it when rotated. �Examples: Bolt Spiral staircase wood screw Corkscrews on light bulbs

Simple Machines � Wheel and axle -- a wheel and axle has a larger wheel (or wheels) connected by a smaller cylinder (axle) and is fastened to the wheel so that they turn together. �When the axle is turned, the wheel moves a greater distance than the axle, but less force is needed to move it. �The axle moves a shorter distance, but it takes greater force to move it. � Examples: Door knob Wagon Toy car Bicycle gears Screw driver

Simple Machines � Pulley -- a wheel that usually has a groove around the outside edge. �This groove is for a rope or belt to move around the pulley. �Pulling down on the rope can lift an object attached to the rope. �Work is made easier since pulling down is assisted by gravity. �Examples: Flag pole Crane Elevators Source: http: //www. edinformatics. com/math_science/simple_machines/pulley. htm Window blinds

Simple Machines � Lever -- a straight rod or board that pivots on a point known as a fulcrum. �The fulcrum can be moved depending on the weight of the object to be lifted or the force you wish to exert. �Pushing down on one end of a lever results in the upward motion of the opposite end of the fulcrum. �Examples: Door on hinges Seesaw Hammer Bottle opener

Classes of Levers � The class of a lever is based on the relative position of the load, effort, and fulcrum. � Levers are classified into 1 st class, 2 nd class and 3 rd class levers.

Classes of Levers � 1 st class: �Crowbar �Scissors

Classes of Levers � 2 nd class: �Nutcracker �Wheelbarrow �Doors

Classes of Levers � 3 rd class: �Tennis racket �Tweezers

Questions about Simple Machines � What is a simple machine? � What are the 6 simple machines? � How does each simple machine work? � How does each machine make work easier? � What are the classes of levers and how do they work? � What is mechanical advantage?