Power and Energy Technology Simple Machines Power and Energy Technology

Behavioral Objectives Students will gain an understanding and be able to identify and use all of the following: Six Simple Machines Four classes of levers Pulleys Fixed Movable Block and Tackle Wheels and Axles Gears Types Bicycle applet

Incline Plane A surface set to an angle to another surface Same amount of work just over a longer distance Resistance Force Inclined Plane

The Wedge Double incline plane Pushes two objects apart Force Effort

The Screw A screw is a shaft that has a in inclined groove along its surface. By rotating the screw (applying a torque), the force is applied perpendicular to the groove, thus translating a rotational force into a linear one. Babylonians developed a "screw" that could elevate water from a low-lying body to a higher one (which later came to be known as Archimedes' screw).

Archimedes' screw

Wheels and Axles Type of lever that rotates around a center fulcrum. Force applied to provide rotation on the axle translates into rotation of the wheel. Force applied to the wheel causes the axle to rotate, which can be used to magnify the force (by, for example, having a rope wind around the axle).

The Lever Consists of a rigid object (bar of some kind) and a fulcrum (Pivot) There are three classes of lever Each offer magnification of the force at another point along the rigid object.

Load Fulcrum First Class Lever Effort

Second Class Lever Effort Fulcrum Load

Third Class Lever Load Fulcrum Effort

Pulleys A wheel with a groove along its edge, where a rope or cable can be placed. principle of applying force over a longer distance Provides mechanical advantage

Fixed Pulley Offers no mechanical Advantage Changes direction of force

Movable Pulley Block and Tackle Combination of fixed and a movable pulleys Can have several pulleys mounted on the fixed and moving axles, further increasing the mechanical advantage.

Block and Tackle Pulleys are assembled together to form blocks Blocks are paired so that one is fixed and one moves with the load A single rope is threaded, or reeved, through the pulleys to provide mechanical advantage

Types of Block and Tackle

Gun Tackle

Double tackle

Gears Are used to change speed, direction and torque Basic gears Spur Gear Bevel Gear Worm Gear Rack and Pinion

Spur Gear Straight-cut gears are the simplest type of gear Gears can be meshed together correctly only if they are fitted to parallel shafts.

Bevel Gear Creates right angles Changes direction of movement

Worm Gear High torque, low speed gear ratio Can create continuous motion

Rack and Pinion Toothed bar or rod. Torque can be converted to linear force by meshing a rack with a pinion: the pinion turns; the rack moves in a straight line

Gear Ratios http://illuminations.nctm.org/ActivityDetail.a spx?ID=178 Gear up this bicycle for speed or power.