Simple Machines Simple Machines Any of various elementary

Simple Machines

Simple Machines • Any of various elementary mechanisms formerly considered as the elements of which all machines are composed and including the lever, the wheel and axle, the pulley, the inclined plane, the wedge, and the screw

Simple machines give us a mechanical advantage over gravity and friction • Gravity: a fundamental physical force that is responsible for interactions which occur because of the attraction of the mass of the earth, the moon, or a planet for bodies at or near its surface • Friction: the force that resists relative motion between two bodies or objects in contact

What is Mechanical Advantage? • The advantage gained by the use of a mechanism in transmitting force; the ration of the force that performs the useful work of a machine to the force that is applied to the machine

Some machines are simpler than others • • • Wedges Levers Pulleys Wheels and axles Screw Inclined plane

Wedge – a piece of a substance (as wood or iron) that tapers to a thin edge and is used for splitting wood and rocks, raising heavy bodies, or for tightening by being driven into something – Examples: axe or hatchet – It is easier to use a wedge, like a knife, to cut an orange rather than try to slice it with my hand

Wedges (NOT a stylish high-heel)

Wedges

Levers – a projecting piece, that transmits and modifies force or motion, by which a mechanism is operated or adjusted – Reduce the amount of energy exerted by lengthening the lever and lengthening the time it takes to exert that energy – Includes a fulcrum: the point on which a lever rests or is supported and on which it pivots – Example: Scissors, pliers

Levers

Pulleys – a wheel used to transmit power by means of a band, belt, cord, rope, or chain passing over its rim – By doubling the distance, we increase the time it takes to raise the weight of the object – Example: window blinds

Pulley

Pulley

Wheels and Axles – Make it easier to move things by overcoming friction – Axle: a pin or shaft on or with which a wheel or pair of wheels revolves – Example: car

Wheels and Axles

Screw – A mechanism that converts rotational motion to linear motion, and a rotational force (torque) to linear force – Most common form: consists of a cylindrical shaft with helical grooves or ridges called threads around the outside – Example: drill

Screws

Inclined Plane • A flat supporting surface tilted at an angle, with one end higher than the other, used as an aid for raising or lowering a load • Example: evacuation slide, loading ramps

Inclined Plane