Wheel and Axle Lever Simple Machines Pulley Screw Wedge Inclined Plane

Would it require more work to take 100, 1kg books to the book room one at a time, or to take them in stacks of 20? Why???

Simple Machine A machine is a device that does work. Machines do not decrease the amount of work done, but they do make work easier.

The magnitude of the force The direction of the force Or both Why are they Useful? They change: The magnitude of the force The direction of the force Or both

A machine is a device that does work A machine is a device that does work. Machines do not increase the amount of work done, but they do make work easier.

Machines make work easier by changing force or distance, or by changing the direction of the force.

There are two major categories of simple machines: the lever and the inclined plane.

Lever or Inclined Plane? Wheel and Axle Lever Lever or Inclined Plane? Pulley Screw Wedge Inclined Plane

The wheel and axle, pulley, wedge, and screw are modifications of the two simple machines.

Example Have you ever tried to unscrew screw from something with your bare hands?

What Did You Do?

You got the proper tool, such as a screw driver

So why is it so much easier to do with the screwdriver than your hand?

The screw driver is an examples of a wheel and axle, The screw or bolt is the axle The handle is the wheel. The tool makes the job easier by changing the amount of the force you exert. Wheel Axle

Simple machines make difficult tasks much easier

WORK MUST BE CONSERVED Win = Wout Fe x de = Fr x dr

EFFICIENCY A measure of how much of the work put into a machine is changed into useful output work by the machine

All machines have efficiencies that are less than 100%. Why?

EFFICIENCY

If a machine outputs 50J of work and you input 100J of work, what is the efficiency of the machine?

A machine has an efficiency of 80% and has a work output of 50J A machine has an efficiency of 80% and has a work output of 50J. What is the work input?

Force applied to the machine EFFORT FORCE Fe Force applied to the machine

Force applied by the machine to overcome resistance RESISTANCE FORCE Fr Force applied by the machine to overcome resistance

The number of times a machine multiplies the effort force MECHANICAL ADVANTAGE The number of times a machine multiplies the effort force

MECHANICAL ADVANTAGE

The force that you put into machine is 15N. The resistance force is 30N. What is the Mechanical Advantage?

The force effort is 10N. The resistance force is 8N The force effort is 10N. The resistance force is 8N. Please calculate the Mechanical Advantage and explain what is interesting about this calculation.

The mechanical advantage is 20. The force effort is 5N The mechanical advantage is 20. The force effort is 5N. What is the force resistance?

IDEAL MECHANICAL ADVANTAGE (for a lever)

IDEAL MECHANICAL ADVANTAGE (for a w&a)

Let's Take a Look at Them

Levers Lever Load Fulcrum

Three classes of lever: First Second Third Crow bar Wheel Barrow Broom Scissors Nutcracker Elbow Can opener Bottle opener Baseball bat

SIMPLE MACHINES LEVER A lever is a simple machine.  It is a board or bar that rests on a turning 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  

SIMPLE MACHINES SCREW   A screw is a simple machine that is made from another simple machine.  It is actually an inclined plane that winds around itself.  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.  

EXAMPLES OF SCREWS Jar Lids Light Bulbs Stools Clamps Jacks Wrenches Key Rings Spiral Staircase

SIMPLE MACHINES WEDGE A wedge is a simple machine used to push two objects apart.  A wedge is made up of two inclined planes.  These planes meet and form a sharp edge.  This edge can split things apart.    

EXAMPLES OF WEDGES Knives Axes Forks Nails

SIMPLE MACHINES INCLINED PLANE A simple machine that is a flat 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

SIMPLE MACHINES WHEEL AND AXLE The wheel and axle is another simple machine.  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 OF WHEEL AND AXLE Cars Roller Skates Wagons Door Knobs Gears in Watches, Clocks, and Bicycles

SIMPLE MACHINES PULLEY This simple machine is made up of a wheel and a rope.  The rope fits on the groove of the wheel.  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 PULLEYS Flag Poles Clothes Lines Sailboat Blinds Crane

The 6 Simple Machines Lever Inclined Plane Pulley Wheel and Axle Wedge Screw

Examples Teeter-totter or seesaw is an example of a class-one LEVER. The balance point, or fulcrum, is somewhere between the applied force and the load. This type of lever (class one) has three parts: the balance point or fulcrum, the effort arm where the force or work is applied, and the resistance arm where the object to be moved is placed. The nail bar is also a lever, but it is a class-two lever (if you use the right end of the nail bar shown in the picture). A class-two lever is a lever with the effort and resistance forces on the same side of the fulcrum. To pry the nail with the right end of the bar shown, the fulcrum is the tip, the nail head applies a resistive force, and at the opposite end is the effort or work. Another example of a class-two lever is a wheel barrow. The wheel chair ramp is an inclined plane. Although the distance up the ramp is greater than the distance straight up, less force is required.

More Examples It can be difficult to understand the usefulness of a machine that increases the effort or force to move an object – that is, decreases advantage. If you keep in mind that machines allow us to optimize force and distance – increasing or decreasing one, while decreasing or increasing the other – this application makes more sense. Basically, the “trade off” for increased force is decreased distance. A fishing pole is a very good example. Explain. … another example is the handbrakes on bicycles. Third Class Lever In this class of levers, the force arm lies between the fulcrum and the load arm. Because of this arrangement, a relatively large force is required to move the load. This is offset by the fact that it is possible to produce movement of the load over a long distance with a relatively small movement of the force arm. Think of a fishing rod! Because of this relationship, we often employ this class of lever when we wish to produce large movements of a small load, or to transfer relatively low speed of the force arm to high speed of the load arm. When a hockey stick or a baseball bat is swung, a third class lever is in effect. The elbow acts as a fulcrum in both cases and the hands provide the force (hence the lower arm becomes part of the lever). The load (i.e. the puck or the ball) is moved at the end of the stick or bat. Example of third class levers are: a fishing pole, a pair of tweezers, an arm lifting a weight, a pair of calipers, a person using a broom, a hockey stick, a tennis racket, a spade, or a shovel.

ORGANIZER SIMPLE MACHINES WHAT IT IS HOW IT HELPS US WORK EXAMPLES LEVER A stiff bar that rests on a support called a fulcrum Lifts or moves loads Shovel, nutcracker, seesaw, crow-bar, elbow INCLINED PLANE A slanting surface connecting a lower level to a higher level Things move up or down it Slide, stairs, ramp, escalator WHEEL AND AXLE A wheel with a rod, called an axel, through its center: both parts move together Doorknob, pencil sharpener, bike Typically, machines are intended to reduce the amount of force required to move an object. But in the process, the distance is increased. A wheel chair ramp is easily visualized example of this relationship. While the amount of effort and strength is reduced (force) the actual distance is significantly increased. Therefore, the amount of actual work is the same. While the typical applications of machines is to reduce effort or force, there are important applications of machines where this is no advantage – that is force is not reduced, or there is actually a decrease in advantage – that is, force is increased. The best example of a machine that provides no advantage is a simple or single pulley. A single pulley only changes the direction of the effort force. A curtain pull is an example.

ORGANIZER SIMPLE MACHINES WHAT IT IS HOW IT HELPS US WORK EXAMPLES PULLEY A grooved wheel with a rope or cable around it Moves things up, down, or across Curtain rod, tow truck, mini-blind, flag pole, crane WEDGE A type of inclined plane with a sharp edge. The wedge moves, the inclined plane stays still. Pushes things apart Axe blade SCREW An inclined plane wrapped around a cylinder. Works with a lever. Raises weights, presses or fastens objects Screws, nuts Typically, machines are intended to reduce the amount of force required to move an object. But in the process, the distance is increased. A wheel chair ramp is easily visualized example of this relationship. While the amount of effort and strength is reduced (force) the actual distance is significantly increased. Therefore, the amount of actual work is the same. While the typical applications of machines is to reduce effort or force, there are important applications of machines where this is no advantage – that is force is not reduced, or there is actually a decrease in advantage – that is, force is increased. The best example of a machine that provides no advantage is a simple or single pulley. A single pulley only changes the direction of the effort force. A curtain pull is an example.

Inclined Plane

Screw A screw is an inclined plane wrapped around a post.

Wedge Two inclined planes make a wedge.

Wheel and Axle Wheel Axle

Pulleys Wheel Rope

3 classes of levers Determined by position of load, fulcrum, and effort

1st Class Lever The claw on a hammer is a lever. We call this kind of lever a first-class lever.

2nd Class Lever A bottle opener is a second-class lever, which means the fulcrum is at the end of the lever and the load is in the middle.

3rd Class Lever A third-class lever has its fulcrum at one end and the load at the other end, with the work you do in the middle. It's how a fishing pole works. You lift just a short distance at the handle, but the end of the pole pops up several feet

A machine that is made up of one or more simple machines. Complex Machine A machine that is made up of one or more simple machines.