## The Balancing Act of the Fulcrum

### Johnny WolfeSanta Rosa District Schools

#### Description

If you have observed people on a seesaw, you may have noticed that the heavier person must sit closer to the fulcrum to balance the seesaw. This is an example of an inverse variation. A seesaw is a type of lever.

#### Objectives

Understands and explains the effects of addition, subtraction, multiplication and division on real numbers, including square roots, exponents, and appropriate inverse relationships.

Uses estimation strategies in complex situations to predict results and to check the reasonableness of results.

#### Materials

-Overhead transparencies, if examples are to be worked on overhead, for Balancing Act of the Fulcrum (See attached file)
-Balancing Act of the Fulcrum (See attached file)
-Balancing Act of the Fulcrum Activity Sheet (See attached file)
-Balancing Act of the Fulcrum Checklist (See attached file)

#### Preparations

1. Prepare transparencies (if teacher uses overhead for examples) for Balancing Act of the Fulcrum Examples. (See attached file.)

2. Have marking pens (for overhead).

3. Have Balancing Act of the Fulcrum Examples prepared and ready to demonstrate to students. (See attached file.)

4. Have enough copies of Balancing Act of the Fulcrum Activity Sheet for each student. (See attached file.)

5. Have enough copies of Balancing Act of the Fulcrum Checklist for each student. (See attached file.)

#### Procedures

Prior Knowledge: Students should be familiar with basic operation skills, such as addition, subtraction, multiplication, division, exponents, fractions, decimals, solving equations, and the 4-step approach to problem solving. (Note: Square roots and exponents will not be covered.)

1. Get students' attention by asking this question: How many of you have ever played on a seesaw? Get their response and then ask this question: Have you ever been thrown up in the air because the person on the other side did not weigh the same as you? Get their responses and then ask this question: Are you more likely to be thrown up in the air if the person opposite you is heavier or lighter? Get their responses.

2. Make the following statement: If you have observed people on a seesaw, you may have noticed that the heavier person must sit closer to the fulcrum to balance a seesaw. This is an example of an inverse variation. A seesaw is a type of lever.

3. Go over the Property of Levers. (See attached file: Balancing Act of the Fulcrum Examples.)

4. Go over Discussion Question 1. (See attached file: Balancing Act of the FUlcrum Examples.)

5. Work example 1 from Balancing Act of the Fulcrum Examples.) (See attached file.) Answer student questions and comments.

7. Work example 3. Emphasize the changing of units. Answer student questions and comments.

10. Distribute the Balancing Act of the Fulcrum Activity Sheet. (See attached file.)

11. Distribute the Balancing Act of the Fulcrum Checklist. (See attached file.) Explain the assessment.

12. The students will write their responses on the activity sheets.

13. Move from student to student, observing the students' work and lending assistance.

#### Assessments

The student worksheet will be assessed according to the checklist: Balancing Act of the Fulcrum. (See attached file.)

#### Extensions

Have students take a yardstick and balance it. Then place a weight at a constant distance on one side. Have the students experiment with different weights and different distances on the opposite side to make the two sides balance.