Simple MachinesObjectives:

To learn about the theory behind Simple Machines

To be able to calculate and understand mechanical advantages gained from using

simple machines

Six Classic Simple Machines

Simple MachinesBefore you start your assignment, we will look at one model that can explain all simple machines. This model will use the concept of work. Since there are different kinds of simple machines and numerous examples of their use in the real world, we will use a box to represent the machine.

Efficiency

• This means we will assume no friction—the work output will equal the work input. Although it is against the laws of physics to have 100% efficiency, it will be useful for you to assume 100% efficiency to help you understand the purpose of the machine. Using simplified models such as this is an important technique in physics.

• The angle between the force and the displacement can vary but it does not affect the real operations of the simple machine. It affects the value of work, but not how the machine does its job. Therefore let us simplify the mathematics and pick 1 = 2 = 0o This makes cos 1 = cos 2 = 1. The force and displacement will be in the same direction.

1 1 1 2 2 2cos cosF r F r

The output force is larger than the input force, but input displacement is more than the output displacement.

1 1 2 2F r F r

In Physics (and life?) Nothing is free.

The displacement is larger than the input displacement, but the input force is larger than the output force.

Efficiency can be defined as the ratio of the useful energy output to the total energy the system started

with initially.

A typical car is approximately 14% efficient, which means that only 14% of the energy stored in the gasoline actually takes you down the road.

Conservation of Energy and Efficiency an Example Problem with a Solution.

A spring-loaded mechanism is designed to shoot a ball straight up into the air, so for kids can practice their batting skills. The spring in the gun has a spring constant of 400 N/m and shoots a light ball of mass 0.1 kg. When fully cocked, the mechanism’s spring is compressed a distance of 10 cm, and the ball reaches a maximum height of 1.2 m above its starting position. What is the efficiency of the mechanism?

Simple Machines

Simple Machines:

Inclined Planes

Wedge

A wedge is closely related to the inclined plane. A wedge can be used to life a heavy load over a short distance or to split things into two pieces.

Screw

A screw is a central core with a thread or groove wrapped around it to form a helix. While turning, a screw converts a rotary motion into a forward or backward motion

Lever

Pulleys and their uses

Block and tackle

Wheel and Axle

Other Elements of Machines:

A game for thought!

http://legacy.mos.org/sln/Leonardo/seven/tank.html

Sketching A Gadgets AnatomyThe Learning Objectives for the project include: Observe a machine closely from several angles while it operates.Identify the elements of machines combined in different gadgets.Show how the moving parts in machines relate to and affect each other.Create a clear diagram of how a machine works.

Possible Materials you should gather include: paper pencils with eraserscopies of the pages for reference.

a selection of small machines with visible working parts (the more you have, the better) carefully look about your home or business here is a list of some examples that might work. There are many others.egg beater, cork screw, car jack, can opener, garlic press, tongs, monkey wrench, hand drill, Vise-Grips, the mechanism from a music box, wind up toy, pencil sharpener, stapler.

Gadget Anatomy ProjectProcedure: Once you have found your machine, examine it in detail. I suggest that you operate the machine watch to see how each part moves.Challenge yourself with the following questions to encourage thought. investigate your own questions as well.

– What is the function of this machine?– How many moving parts does it have?– How are the moving parts connected to each other?– What does each moving part do in the machine?– Which parts are elements of machines?

Place the machine at rest. Begin sketching diagrams of your machine. Draw the machine from your own point of view first. Then rotate it and draw it from a different perspective or points of view to show all working parts that are possible.When the diagrams are completed, you should add arrows and written notes to indicate directions of motion for each part, label the elements of machines involved, and explain its connections.After you are finished with this drawing, display and explain the diagrams to your instructor via a video tape, that you submit as a capstone project.

The Way Things Work by David Macaulay

Finding detailed plans

Which elements of machines do you see in each gadget? Click on only the ones you see.

Design a machine that makes a motion.A simple machine capstone exercise.

I hope that we have been able to keep you from rage!

Good Luck as you move forward on the next project and assignment from your instructor.