20 questions. Physical science.

Includes index

Simple yet helpful -- What is work? -- How common are simple machines? -- What is a lever? -- What does a lever do? -- Is a seesaw a lever? -- Are the wheels on my bike a simple machine? -- How do we use wheels and axles? -- What is a pulley? -- How does it work? -- Why do we need pulleys? -- Is a ramp a simple machine? -- What kind of work does an inclined plane help us do? -- Are there other kinds of inclined planes? -- Is a doorstop a wedge? -- What are some other wedges? -- What is a screw? -- How does a screw work? -- Are there other simple kinds of machines? -- How long have people been using simple machines? -- Do we still need simple machines today?

Presents an introduction to the basic principles of such simple machines as the lever, pulley, ramp, wedge, and the screw, and describes how they are used in everyday life