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

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

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

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 Inclined Plane Wheel & Axle Screw Pulley Wedge

Compound Machine: two or more linked simple machines Compound Machines Link to Rube Goldberg video from online. I downloaded one and inserted it into my presentation, but I can’t post that. 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:

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