Human mechanic. (Hands-On Activity).

What does it take to build bionic body parts? Here's an activity to find out. Follow the steps below to devise a "bionic" arm that could lift a quarter from the floor to the height of your desk. The arm must work in the same way your bones and muscles do.

Step 1: Research

Investigate how muscles work to move the bones in your body. Identify the muscles and bones in your arm. How do they work?

Step 2: Develop

Follow these three guidelines:

* Your machine must have at least three parts: one that acts like a muscle, one like a bone, and one like a joint.

* You can use human power to move the "muscle."

* Your machine only has to lift the quarter from the floor to the height of the desk--it does not have to drop the quarter onto the desk.

Step 3: Brainstorm

Think and list objects that could act as muscles (spring, twisted string, etc.), bones (a ruler, perhaps), and joints. Also, what will you need to make the quarter stay on the arm?

Step 4: Choose your materials

Review your lists. What objects would you combine to create the arm? Draw your design.

Step 5: Build and test

Build your machine. Test it. If it doesn't work, review your methods and materials. Try again.

Bonus: Advanced development

Alter your machine so it does drop the quarter onto your desk.