Simple Machines - Gabrielse

Simple Machines Machine: an object that changes either the magnitude or direction of a force Simple Machines There are six simple machines: lever inclined plane Machines make life easier.

wedge Without simple machines wheel & axle there would be no other pulley machines. screw All other machines are made out of simple machines.

Mechanical Advantage (how machines make life easier) Double a force by using a machine with a mechanical advantage of two! Fr MA Fe effort force (Fe): the force exerted on a machine resistance force (Fr): the force exerted by a machine

Efficiency Work is input (Wi) to a machine when an effort force (Fe) is applied over a distance (de). Wi = Fede Wo efficiency 100%

Wi Work is output (Wo) from a machine when it exerts a resistance force (Fr) over a distance (dr). Wo = Frdr Ideal Machines (perfect machines) input work (Wi) = output work (Wo) efficiency = 100%

de IMA dr Ideal Mechanical Advantage No real machine is perfectly efficient! Lever (a rigid object pivoting on a fulcrum)

Three types of levers: 1st class lever: fulcrum between Fe & the load 2nd class lever: the load between Fe & the fulcrum 3rd class lever: Fe between the load & the fulcrum Fe Fe Fe

load load load Fr Fr

Fr 1st class lever 2nd class lever 3rd class lever Lever Examples

Crowbar (1st Class Lever Example) Fe Fr Wheel & Axle Wheels rotate around an axle.

Wheel Examples Well Wheel Fe Fr Pulley

A pulley is a wheel with a rope running over it Pulley Examples Inclined Plane A slanted surface or ramp Reduces the force required to move objects

Inclined Plane Examples Wedge A wedge is usually a triangle shape with a sharp point. A wedge is used to split, secure, or lift. Applying a force to one end pushes the wedge between

something The pictured wedge is designed to split wood when hit with a sledge hammer Wedge Examples Wedges that split: teeth knives zippers

Wedges that secure: doorstops nails Wedges that lift: shims golf wedges Screw (a helical inclined plane)

A screw is an inclined plane twisted around an axis. Screw Examples All 6 Simple Machines Lever

Pulley Inclined Plane Screw Wheel & Axle Wedge

Compound Machines Compound Machine: two or more linked simple machines The mechanical advantage of a compound machine is the product of the component simple machines mechanical advantages. Notes: 7. Machine: an object that makes transferring energy easier by changing either the

magnitude or direction of a force A. effort force (Fe): the force exerted on a machine B. resistance force (Fr): the force exerted by the machine C. mechanical advantage (MA): the ratio of the resistance force to the effort force F i. MA r Fe D. input work (Wi): the work done to the machine i. Wi = Fede E. output work (Wo): the work done by the machine

i. Wo = Frdr W F. efficiency o x 100% Wi G. ideal (perfect) machines i. input work (Wi) = output work (Wo) ii. ideal efficiency = 100% d iii. ideal mechanical advantage (IMA): IMA e dr

8. Simple Machines A. lever: a rigid object pivoting on a fulcrum B. wheel & axle: a wheel turning around an axle C. pulley: a wheel with a rope running over it D. inclined plane: a ramp E. wedge: a sharp triangular object F. screw: an inclined plane wrapped around a shaft 9. Compound Machines A. two or more linked simple machines B. MA = (MAmachine 1)(MAmachine 2) ()

Your Turn Chapter 10 Practice Problems (p. 238): 13-16

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