If you have access to an old-fashioned pencil sharpener, with the crank coming out the side, you may want to try this experiment. Besides the pencil sharpener, you will also need several books and a long piece of strong twine.1) Mount the pencil sharpener on a table or other surface. (You can have someone hold it down firmly for you.) Take the cover off so that the axle is exposed.2) Tie the twine around the books so they are secure. Put the books on the floor below the pencil sharpener and tie the other end of the twine to the axle of the pencil sharpener.3) Turn the crank on the pencil sharpener to raise the books off the floor until they are level with the table top. Note the effort it took.4) Try turning the crank closer to the middle of it. Can you raise the books? Explain the difference, using the terms “torque”, “force”, “distance”, and “mechanical advantage”.5) Now untie the twine from the pencil sharpener, put the books back on the floor, and then raise them up to table level by hand, holding the end of the twine. (You might have to stand on a chair for this one!)6) Which method was easier? Can you explain why?
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