Lever A rigid bar that is free to pivot on a fixed point.

PARTS OF A LEVER The Effort Arm---- where effort is applied (work input) The Resistance Arm--the part of a lever that moves a weight. (work output) The Fulcrum-- fixed point on which the lever pivots EA RA F

MECHANICAL ADVANTAGE OF A LEVER MA (lever) = Le / Lr Length of the effort arm / length of the resistance arm Le Lr

1st Class Lever The fulcrum is between the effort Force and the resistance force (weight). It multiplies the EF but decreases the distance the object moves. Crowbar--you push down farther then the nail goes up. Seesaw, pliers, scissors, crowbar EF R F

2nd Class Lever It multiplies EFover a greater distance the resistance force is lifted in the same direction as the Effort force. A wheelbarrow The resistance is the weight in the wheelbarrow. The fulcrum is the wheel The EF is the handles you lift up on. Doors, bottle openers EF R EF R F

3rd Class Lever They reduce the effort force required but multiplies the distance the resistance is moved. The Resistance force is always farther away from the fulcrum then the effort force is. Fishing pole, tweezers, shovels, baseball bat, hammer RF EF

Pulleys A rope , belt, or chain wrapped around a grooved wheel. It changes the direction or the amount of force. Fixed pulley A pulley attached to a structure. MA = changes the direction of the force which makes the effort easier. Movable pulley Pulley is attached to the object being moved. MA = it multiplies the effort force. The more ropes you have on a pulley the easier it is to lift a greater resistance, but it is moved over a longer distance. (takes more rope)

Wheel & Axle Two circular objects of different sizes. Wheel is larger Axle is smaller The wheel always moves a greater distance then the axle. The force applied to the wheel is multiplied when transferred to the axle. MA = radius of wheel / radius of Axle (Rw / Ra) If wheel is 4 times bigger then axle, every time you turn the wheel once you multiply the force 4 times. Ferris wheels, gears, wrenches, door knobs, bicycles.

Inclined Planes A straight slanted surface. Ramps They decrease the amount of force needed to move an object but increases the distance the force is applied. MA increases as the slant of the plane decreases. MA = LR / HR Farm plows,door locks

Screws An inclined plane wrapped around a central bar. As it rotates it moves a distance up or down. It multiplies effort force through a longer distance. MA = The closer the threads are the longer the effort is applied, but it takes left effort to move. Corkscrew, nut & bolt, jar lids, c-clamps. Screws

Wedges An inclined plane that moves. MA =The longer and thinner the wedge is the less effort force is needed to move the wedge. MA = LW / WW A sharp axe splits better then a dull axe. Knife, zippers, axe, keys, locks.