Questions: Choosing Materials

Question 1

A hammer has a steel head and a wooden handle. Why are two different materials used instead of making the whole hammer from one material?

• A. Because they ran out of steel
• B. Because the head needs to be hard and heavy to drive nails, while the handle needs to be light and absorb shock for comfortable gripping
• C. Because wood is stronger than steel
• D. Because all tools must use exactly two materials

Answer: (B)

Each part of the hammer faces different demands. The head must be hard enough not to dent when hitting nails and heavy enough to deliver force. Steel meets those needs. The handle must be light (so the hammer is not too heavy), absorb shock (so your hand does not sting), and provide good grip. Wood meets those needs. Using steel for the handle would make it too heavy and painful to use. Using wood for the head would not drive nails.

Question 2

The strongest material is generally the best choice for an engineering project.

• T. True
• F. False

Answer: False

Strength is only one property engineers consider. A bridge needs strong materials, but a rain jacket needs waterproof, flexible materials — strength is secondary. A packaging engineer needs lightweight, cushioning materials. A good engineer matches material properties to the specific needs of each design.

Question 3

Name three properties of materials that engineers consider when choosing what to build with.

Model answer: Strength, weight, and water resistance (also acceptable: flexibility, cost, heat resistance, durability, appearance, environmental impact, availability).

Material selection requires balancing many properties. A material that is strong but heavy might not work in a design that needs to be carried. A material that is waterproof but brittle might not work in a design that needs to flex. Engineers evaluate materials against the full list of requirements, not just one property.