# Girls vs. Guys: Center of Gravity

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#### Updated on Jun 12, 2013

Grade Level: 6th to 8th; Type: Physics

### Objective:

This science project examines whether males or females are more likely to have a higher center of gravity.

### Research Question:

• How does your sex affect the location of your center of gravity?

The location of your center of gravity affects how well you can balance or play various sports. But do girls and guys have different centers of gravity? This experiment will let you find out.

### Materials:

• Two chairs
• Measuring tape
• Two bathroom scales
• Six-foot plank, at least 6 inches wide
• Several volunteers, male and female
• Calculator (optional)

### Experimental Procedure

1. Put the two chairs about five feet apart, facing each other.
2. Put one scale on each chair.
3. Lay the board across the two chairs so that it rests on both of the scales. Adjust board back and forth until the reading on the two scales is exactly the same.
4. Measure the length of the board that lies between the two scales, from the edge of one scale to the edge of the other. (This measurement should include only the unsupported part of the board.)
5. Calculate the center of the unsupported part of the board, and mark this location with a piece of masking tape.
6. Instruct a volunteer to lie on the board, stomach up. Adjust the volunteer’s position until the reading on the two scales is exactly the same.
7. Put a piece of masking tape on your volunteer’s body, directly above where the masking tape is on the board. This is the volunteer’s center of gravity.
8. Measure the distance between the bottoms of the volunteer’s feet and the masking tape.
9. Measure the volunteer’s height, and divide it by two to find the midpoint on the volunteer’s body.
10. Repeat this process with an equal number of male and female volunteers.
11. Analyze your data. Group your volunteers based on whether their centers of gravity are above, below, or exactly at their midpoints. Do you see a relationship between males, females, and their centers of gravity?

Terms/Concepts: center of gravity; how does your center of gravity affect your balance?

References: First Place Science Fair Projects for Inquisitive Kids, by Elizabeth Snoke Harris, pp. 87-88 (Lark Books, 2005).

Keren Perles has worked as an educational writer, editor, teacher, and tutor of all ages. Her experience spans the subject areas, from science and math, to English and the Hebrew language.