Simple machines / by D.J. Ward ; illustrated by Mike Lowery.
"Machines help make work easier, like when you need to lift something heavy or reach way up high. There are six simple machines: the lever, the wheel and axle, the pulley, the ramp, the wedge, and the screw. Can you adjust a seesaw to lift an elephant? What happens when you combine two or more...
New York, NY :
Harper, an imprint of HarperCollins Publishers,
Walker Library - Curriculum Collection - Juvenile - 3rd Floor
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