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- 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 Work and Power
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 EASIER A 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. dEdL Mechanical Advantage Divide the distance dEfrom the input force (effort) to the fulcrum by the distance from the fulcrum to the output force (load).
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. RADIUS OF WHEEL RADIUS OF AXLE Divide the radius of the wheel by the radius of the axle. MECHANICAL ADVANTAGE
Pulley *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. *Examples of where pulleys can be used: ·Flag Poles ·Clothes Lines ·Sailboat ·Blinds ·Crane HOW IT MAKES WORK EASIER A 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 Pulleys Movable Pulley Fixed Pulley Pulley System The mechanical advantage of a pulley system is equal to the number of sections of rope pulling up on the object. The mechanical advantage of a fixed pulley is 1. The mechanical advantage of a movable pulley is 2.
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 EASIER 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 AN INCLINE PLANE. LENGTH of INCLINED PLANE HEIGHT OF INCLINED PLANE The length of the inclined plane divided by its height. 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 EASIER A 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 LENGTH OF WEDGE HEIGHT OF WEDGE The length of the wedge divided by its height. This increases as the wedge becomes longer and thinner.
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 EASIER A 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. LENGTH OF INCLINED PLANE The length of the inclined plane wrapped around the screw divided by the length of the screw. LENGTH OF SCREW MECHANICAL ADVANTAGE
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. GEARS 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. Examples of where gears are used. Bicycles Cars Wind up toys and clocks 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. http://www.dynamicscience.com.au/tester/solutions/hydraulicus/gears.htm
Chapter 14 Preview Page pg 418 figure 9 pg 420 figure 13 A. Copy And Label The Diagrams Of Simple Machines pg 423 figure 17 pg 422 figure 16 C. Read pg. 426 Why do you think they include this section in the chapter? ______________________________________________________________________________________________________________________________________________________ B. Look at the pictures throughout Chapter 14 and list some activities that people do using Simple Machines 1. ________________________________ 2. ________________________________ 3. ________________________________4. ________________________________5. ________________________________
CREDITS http://www.mos.org/sln/Leonardo/InventorsToolbox.html http://atlantis.coe.uh.edu/archive/science/science_lessons/scienceles1/finalhome.htm http://science.howstuffworks.com/transport/engines-equipment/pulley.htm?printable=1 http://sln.fi.edu/qa97/spotlight3/spotlight3.html