Simple Machines

Essential Question: What are simple machines and how do they work?

Vocabulary• Power• Work• Efficiency• Input Force• Mechanical

Advantage

• Output Force• Compound

Machine• Simple Machine

• Inclined Plane• Lever• Pulley• Screw• Wedge• Wheel and Axle

Work and Power• Work- is done when a force

makes an object move in the same direction as the force that is applied

• Power- How quickly work is done

Efficiency- the ratio of output work to input work

Input Force- The force that you apply on a machine (also called Effort).

Output Force- The force that the machine applies to the Load.

Mechanical Advantage- the number of times that a machine increases the input force.

Lever*Lever: A lever is a simple machine. A lever is a stiff rod or plank that turns around a point.This turning point is called the fulcrum. An object that a lever moves is called the load. The closer the object is to the fulcrum, the easier it is to move.

*Examples of Levers:·A hammer is a lever when it is used to pull a nail

out of a piece of wood. ·Bottle openers ·Crow bars Levers are one of the basic tools that were probably used in prehistoric

times. Levers were first described about 260 BC by the ancient Greek mathematician Archimedes (287-212 BC). HOW IT MAKES WORK EASIERA lever is a simple machine that makes work easier for use; it involves moving a load around a pivot using a force. Many of our basic tools use levers, including scissors (2 class 1 levers), pliers (2 class 1 levers), hammer claws (a single class 2 lever), nut crackers (2 class 2 levers), and tongs (2 class 3 levers).

MECHANICAL ADVANTAGE OF A LEVER.

Divide the distance dE from the input force (effort) to the fulcrum by the distance from the fulcrum to the output force (load).

dE dL Mechanical Advantage

Wheel and Axle*Wheel and Axle: The wheel and axle is another

simple machine. This machine is composed of two round objects of different sizes that are attached so they turn together. The axle is a rod that goes through the wheel. This lets the wheel turn. It is easy to move things from place to place with wheels and axles.

*Examples : ·Cars ·Roller Skates ·Wagons ·Door Knobs ·Gears in Watches,HOW IT MAKES WORK EASIER

In this machine a wheel or spoke is locked to a central axle so that when one is turned the other must turn. A longer motion at the edge of the wheel is converted to a shorter more powerful motion at the axle. In reverse, a short powerful force at the axle will move the wheel's edge a greater distance.

MECHANICAL ADVANTAGE OF A WHEEL AND AXLE.Divide the radius of the wheel by the radius of the axle.

RADIUS OF WHEEL

RADIUS OF AXLE

MECHANICAL ADVANTAGE

Pulley

*Examples of where pulleys can be used:·Flag Poles ·Clothes Lines ·Sailboat ·Blinds ·Crane

*Pulley: This simple machine is made of a grooved wheel with a rope wrapped around it.One part of the rope is attached to the load. When you pull on one side of the pulley, the wheel turns and the load will move. Pulleys let you move loads up, down, or sideways. Pulleys are good for moving objects to hard to reach places. It also makes the work of moving heavy loads a lot easier.

HOW IT MAKES WORK EASIERA single pulley simply reverses the direction of a force. When two or more pulleys are connected together, they permit a heavy load to be lifted with less force. The trade-off is that the end of the rope must move a greater distance than the load.

Types of PulleysFixed Pulley Pulley SystemMovable Pulley

The mechanical advantage of a fixed pulley is 1.

The mechanical advantage of a movable pulley is 2.

The mechanical advantage of a pulley system is equal to the number of sections of rope pulling up on the object.

Inclined Plane*Inclined Plane:An inclined plane is a simple machine. It is a flat sloped surface that is higher on one end. You can use this machine to move an object to a lower or higher place. Inclined planes make the work of moving things easier. You would need less energy and force to move objects with an inclined plane.

*Examples of Inclined Planes:·Ramp ·Slanted Road ·Path up a Hill ·Slide

HOW IT MAKES WORK EASIERThe inclined plane is a plane surface set at an angle, other than a right angle, against a horizontal surface. The inclined plane permits one to overcome a large resistance by applying a relatively small force through a longer distance than the load is to be raised.

MECHANICAL ADVANTAGE OF AN INCLINE PLANE.

The length of the inclined plane divided by its height.

LENGTH of INCLINED PLANE

HEIGHT OF INCLINED PLANE

MECHANICAL ADVANTAGE

Wedge

*Wedge: A wedge is an inclined plane that moves. It is a simple machine used to push two objects apart. A wedge is made up of one or two inclined planes. These planes meet and form a sharp edge. This edge can split things apart. *Examples of

wedges:·Knives ·Axes ·Forks ·Nails

HOW IT MAKES WORK EASIERA wedge converts motion in one direction into a splitting motion that acts at right angles to the blade. Nearly all cutting machines use the wedge. A lifting machine may use a wedge to get under a load.

MECHANICAL ADVANTAGE OF A WEDGE.

MECHANICAL ADVANTAGE

The length of the wedge divided by its height. This increases as the wedge becomes longer and thinner.

LENGTH OF WEDGE

HEIGHT OF WEDGE

Screw*Screw: A screw is a simple machine that is made from another simple machine. It is actually an inclined plane wrapped around a cylinder or post. A screw has ridges and is not smooth like a nail. Some screws are used to lower and raise things. They are also used to hold objects together. *Where

would I find an example of a screw?·Jar Lids ·Light Bulbs ·Stools

·Clamps ·Jacks ·Wrenches ·Key Rings ·Spiral Staircase

HOW IT MAKES WORK EASIERA screw is a modified inclined plane. The inclined plane is a plane surface set at an angle, other than a right angle, against a horizontal surface. The inclined plane permits one to overcome a large resistance by applying a relatively small force through a longer distance than the load is to be raised.

MECHANICAL ADVANTAGE OF A SCREW.

The length of the inclined plane wrapped around the screw divided by the length of the screw.

LENGTH OF INCLINED PLANE

LENGTH OF SCREW

MECHANICAL ADVANTAGE

Gears have many uses in our lives. They are used to :- multiply or reduce speed and force;- change the direction of motion;- transmit a force over a distance.

GEARS

http://www.dynamicscience.com.au/tester/solutions/hydraulicus/gears.htm

However, it can decrease the amount of *force* needed to perform an action. Often, it is an inability to generate enough force that makes a job impossible, not an inability to do enough work. Therefore, gearing can make certain tasks possible for a human to perform.For example, a human ordinarily could not lift a 1500-kg car off the ground, because they couldn't exert enough force. But with the right gearing, even a child could lift the car. The gearing would enable them to exert a small force over a large distance to perform the task.

Examples of where gears are used.BicyclesCarsWind up toys and clocks

Two adjacent gears will have opposite directions of rotation. They also have seen that the number of times a gear goes around depends on how big the gears next to it are.

A. Copy And Label The Diagrams Of Simple Machines

B. Look at the pictures throughout Chapter 14 and list some activities that people do using Simple Machines1. ________________________________2. ________________________________3. ________________________________4. ________________________________5. ________________________________

pg 420 figure 13

Chapter 14 Preview Page

C. Read pg. 426Why do you think they include this section in the chapter?______________________________________________________________________________________________________________________________________________________

pg 418 figure 9

pg 422 figure 16

pg 423 figure 17

http://www.mos.org/sln/Leonardo/InventorsToolbox.html

http://sln.fi.edu/qa97/spotlight3/spotlight3.html

http://science.howstuffworks.com/transport/engines-equipment/pulley.htm?printable=1

http://atlantis.coe.uh.edu/archive/science/science_lessons/scienceles1/finalhome.htm

CREDITS