DOUBLE TAP TO ZOOM WITH PHONE OR TABLET Science Content Like the inclined plane, the wheel and axle allows an individual to use less force to move an object be- cause the force is spread out over a greater distance. In this activity, the smaller wheel requires more force to move the bucket than the larger wheel because the larger wheel spreads the force over a greater distance; however, turning the smaller wheel requires less force than turning the rod itself. Teachers can point out the distance the handle moves on the large circle compared with the distance the handle on the small wheel must travel. If children are interested, they can stretch cord around the edges (circumfer- ences) of both circles and compare the lengths. Mathematics Content An interesting mathematical component of this ac- tivity is for children to compare the number of turns of the large versus the small wheel needed for the bucket to reach the water. Although the large wheel itself moves much farther than the small wheel, it does not move the bucket any farther than the small wheel does because one rotation of the wheel, independent of its diameter, completes one rotation of the rod. Therefore, both wheels must rotate the same number of times before the bucket reaches the water. of engineering designs in areas such as the automo- bile industry. Teachers can help children understand the importance of this technology by asking ques- tions throughout the day when children encounter examples of the wheel and axle, as in the following: • How would you move the wagon if it didn’t have wheels? • Is it easier to move this big block by pushing it along the ground or by pushing it on the wagon? • How could we open the door without the doorknob? Comments and Questions to Support Inquiry • How many times do you need to turn the big wheel before the bucket reaches the water? How many times do you need to turn the little wheel? • Does the bucket move farther when you move the big wheel one time around versus the little wheel? Let’s put a stick in the well and mark the distance the bucket moves when we move each wheel one complete turn. • What makes the bucket move? Misconception Alert Connections to Technology and Engineering The wheel and axle is itself an example of technology that has evolved over thousands of years yet is still a fixture of modern life. It is an important component Not every wheel mounted to a rod constitutes a wheel and axle. In a true wheel and axle, the rod and wheel are firmly attached so that when one rotates, so does the other. COPYRIGHTED MATERIAL ST E M lE aR n I ng c E n T E R S 25