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Overview: In this investigation of simple machines (wheel-and-axle), students modify a paper clip to do work with less effort.
Booklink: How Do You Lift a Lion? by Robert E. Wells, Albert Whitman and Company, Illinois, 1996. ISBN 0-8075-3421-8
Science Activity Link: In this experience students investigate changes to a paper clip that convert it into a wheel-and-axle simple machine to do work with less effort.
Objective: Students will construct two simple wheel-and -axle simple machines, describe their parts, and demonstrate the advantage of using one to do work.
Science Processes and Content: Processes-Observing, inferring, measuring, modeling Content-Simple machines, wheel-and-axle, force, lever, effort, motion, distance, fulcrum, work
National Science Education Standards: Unifying Concepts and Processes, (1) Science as Inquiry, (2) Physical Science, (5) Science and Technology
Materials: Standard paper clips (one per student)
Procedure:
1. Provide each student with a paper clip. Ask them to straighten it as much as they can into one long piece of metal.
2. Now challenge them to hold (with one hand) one end of the straightened clip as tightly as they can between their index finger and thumb while attempting to twist or turn the other end with with their other hand's index finger and thumb. Most will find it very difficult to do!
3. Next, have them bend the straightened clip into two right angles, like this
 , shaped like a crank.
4. Again challenge them to hold as tightly as possible one end of the crank-shaped clip between the index finger and thumb. Now rotate the other end like a crank. Everyone will find it very easy to turn--one of the advantages of a simple machine.
5. Explain to the students the wheel-and-axle simple machine they just investigated, e.g.
resistance--where the clip is held tightly
force--applied where your fingers turn the crank
wheel--the crank's circumferance; the circle of the turning crank
axle--the metal clip on which the wheel turns
fulcrum--the center of the axle
work--force X distance
simple machine--the basic element of a complex machine
What made the crank-shaped clip easier to turn? To turn the straight clip (if it was done at all) required the application of a lot of force or effort through a short distance (the radius of the clip). Turning the crank clip, required only the application of a little force but through a longer distance, the radius of the crank, which made it seem easier. One of the purposes of both simple and complex machines is to make work easier.
By the way, if a lot of force was put into trying to turn the straightened clip and it still didn't turn between tightly held fingers, no work was done. Work is defined a force through distance. If there is a lot of force but no distance is achieved, no work is done--no matter how hard you tried!
6. Read and discuss the book, How Do You Lift a Lion, which focuses on the workings of levers, wheel-and-axles, and pulleys.
Safety: None
Related Books:
Machines by David Glover, World Book/Two-Can, 1997. ISBN 0-7166-4706-0
Mike Mulligan and His Steam Shovel by Virginia Lee Burton, Houghton Mifflin Company, Boston, 1939. ISBN 0-395-25939-8 |
