Gravity and Stability

Grade Level

9th Grade

Duration

45 minutes

Unit

Biomechanics in Motion (Lesson 3 of 4)

---

Learning Objectives

By the end of this lesson, students will be able to:

• Define and explain the concepts of center of gravity, balance, and stability.
• Describe how leverage affects movement and stability in physical tasks.
• Apply understanding of center of gravity and stability to analyze real-world movements.

Common Core State Standards Alignment

Though Common Core primarily focuses on ELA and Math, this Health/Science-integrated lesson aligns with CCSS literacy standards for science and technical subjects:

• CCSS.ELA-LITERACY.RST.9-10.3
  Follow precisely a complex multistep procedure when carrying out experiments or performing technical tasks, attending to special cases or exceptions defined in the text.

• CCSS.ELA-LITERACY.RST.9-10.7
  Translate quantitative or technical information expressed in words in a text into visual form and translate information expressed visually or mathematically into words.

• CCSS.ELA-LITERACY.SL.9-10.1
  Initiate and participate effectively in a range of collaborative discussions with diverse partners on grades 9-10 topics, texts, and issues, building on others' ideas and expressing their own clearly.

---

Materials Needed

• Meter sticks or yardsticks (1 per group of 4-5 students)
• Small balance boards or sturdy cardboard for balance tasks (1 per group)
• Various classroom objects of different weights and shapes (e.g., books, balls, rulers)
• Whiteboard and markers
• Worksheets with diagrams showing center of gravity and leverage examples
• Dyslexia-friendly handouts (with clear fonts, larger print, bullet points)
• Timer or stopwatch

---

Success Criteria

• Students can accurately identify the center of gravity in simple objects.
• Students demonstrate through activity how shifting the center of gravity impacts balance.
• Students verbalize or write explanations of how leverage affects movement and stability.
• Students engage appropriately in group discussions and activities.

---

Lesson Breakdown

1. Engage (5 minutes)

Begin with a brief demonstration of balance using a meter stick. Hold the meter stick horizontally on one finger and ask the class, “Where should I place my finger to keep it balanced?”

• Guide students to suggest the midpoint, connecting to center of gravity.
• Briefly introduce the terms: center of gravity, balance, and stability.

2. Explore (15 minutes)

Hands-On Activity: Finding the Center of Gravity

• Divide students into groups of 4-5.
• Each group will use meter sticks and classroom objects.
• Task: Balance the objects on the meter stick and find its center of gravity by moving the fulcrum point.
• Students record observations: Where is the center of gravity for symmetrical vs. asymmetrical objects?
• Next, place objects on balance boards—experiment by shifting weight to see effects on stability.

Differentiation:

• Provide step-by-step illustrated guides for groups with diverse learners.
• Offer peer support and allow extra time if needed.

3. Explain (10 minutes)

Bring students back for a whole-class discussion.

• Use the whiteboard to diagram how center of gravity works in humans and objects.
• Discuss leverage: how longer or shorter lever arms affect ease of movement and stability (e.g., pushing a door near hinges vs. near the handle).
• Use student examples from the activity to connect theory to observed behavior.

4. Elaborate (10 minutes)

Application Activity: Real-World Movements

• In pairs, students brainstorm examples of balance and leverage in sports or daily life (e.g., gymnastics, skateboarding, carrying heavy backpacks).
• Each pair shares one example explaining center of gravity and leverage concepts involved.
• Optionally, invite students to demonstrate a pose or movement showing balance and center of gravity.

Extension for Advanced Learners:

• Challenge these students to calculate how shifts in center of gravity might affect stability numerically using sample weights and distances (introduce simple physics concepts connecting force and torque).

5. Evaluate (5 minutes)

Exit Ticket:

• Write a brief answer to:
  “Explain why a tightrope walker carries a long pole and how it affects their center of gravity and balance.”
• Collect responses to assess understanding.

---

Differentiation Strategies

• Use visual aids with dyslexia-friendly font (e.g., OpenDyslexic), high contrast, and spacing on all handouts.
• Break down complex terms with clear definitions and relatable analogies.
• Use multimodal teaching: verbal explanation, visual diagrams, and kinesthetic activities.
• Pair struggling students with peer mentors during activities.
• Provide sentence starters for exit ticket to support written responses.

---

Extension Activities for Advanced Learners

• Explore torque calculations: How does varying the length of lever arms or weight change rotational forces?
• Research and present on athletes who use biomechanics principles in their training for stability and balance (e.g., figure skaters, divers).
• Design a simple experiment to measure the effect of different weights on balance stability using homemade balancing tools.

---

Classroom Management Tips

• Keep groups small to ensure active participation.
• Monitor safety during balance board tasks.
• Use timer to keep pace, ensuring adequate time for exploration and reflection.

---

Reflection & Next Steps

This lesson prepares students for the next unit lesson: “Biomechanical Movements in Sports Performance” where they will analyze complex movements building on balance and leverage concepts.

Students should leave with a concrete understanding of how center of gravity and leverage affect stability and motion, foundational for future study in health, sports science, and physics.

---

End of lesson plan.