# Simple Machines - sca.district70.org Simple Machines CHAPTER 4 SECTION 3 Key Concepts What are the six kinds of simple machines, and how are they used? What is the ideal mechanical advantage of each simple machine? What is a compound machine? Key Terms Incline Plane Wedge

Screw Lever Fulcrum Wheel and axle Pulley Compound Machine Simple Machine

There are six basic kinds of simple machines: The incline plane The wedge The screw The lever The heel and axle

The pulley Incline Plane Incline Plane: a flat, sloped surface. A ramp: Makes it easier for lifting upwards. How it works: Allows you to exert your input force over a longer distance. Your input force is less than the output force

Mechanical advantage: You can determine the ideal mechanical advantage of advantage of an inclined plane by dividing the length of the incline by its height. Ideal Mechanical advantage = Length of incline/Height of incline Wedge Wedge: a device that is thick at one end and tapers to a thin edge at the other end. How it works:

Axe or knife When you use a sedge, instead of moving an object along the inclined plane, you move the inclined plane itself. The handle of an axe exerts a force. The force pushes the wedge down the wood at a 90 degree angle. Mechanical advantage: The mechanical advantage of a wedge is determined by dividing the length of the wedge by its width. Screws Screw: an incline plane wrapped around a cylinder.

The spiral incline plane forms the wedge. How it works: When you twist a screw into a piece of wood, you exert an input force on the screw. The output force is exerted on the object twisted into or onto. Bolts, light bulbs, and jar lids. Mechanical advantage: The closer the threads (wedges) of the screw, the greater the mechanical advantage. The ideal mechanical advantage of a screw is the length around the threads divided

by the length of the screw. Levers Lever: a ridged bar that is free to pivot, or rotate, on a fixed point. How it works: Fulcrum: The fixed point that a lever pivots around. Think about as paint can opener: The opener rest on the fulcrum. When you push down, you exert an input force on the handle.

The opener pivots on the fulcrum. Mechanical advantage: The ideal mechanical advantage of a lever is determined by dividing the distance from the fulcrum to the input force by the distance from the fulcrum to the output force. Wheel and Axle Wheel and Axle: a simple machine made of two circular or cylindrical objects fastened together that rotate about a common axis. The screw driver How it works:

When you use a screw driver, you apply an input force to turn the handle, or wheel. Because the wheel is larger than the shaft, or axle, the axle rotates and exerts a larger output force. Mechanical Advantage: You can find the ideal mechanical advantage of a wheel and axle by dividing the radius of the wheel by the radius of the axle. Mechanical advantage = Radius of wheel/Radius of axle Pulley Pulley: a simple machine made of grooved wheel with a rope or cable wrapped around it.

How it works: Input force is at the end of a rope where you are pulling The output force pulls up on the object you want to move. Mechanical advantage: The ideal mechanical advantage of a pulley is equal to the number of sections of rope that supports the object. Simple Machines of the Body Lifting levers:

Most of the machines in your body are livers that consist of bones and muscles. Working wedges: Your incisors. Compound machines Compound Machine: a machine that utilizes two or more simple machines. The ideal mechanical advantage of a compound machine is the product of the individual ideal mechanical advantages of the simple machines that make it up