Physics · Secondary 4

Active learning ideas

Center of Gravity and Stability

Active learning works for this topic because students physically manipulate objects to see abstract concepts like balance and stability. When they balance irregular shapes or test bases, they build direct evidence to replace misconceptions about geometric centers and uniform mass distribution.

• MOE Syllabus Outcomes
• MOE: Turning Effects of Forces - S4

• 25–45 min
• Pairs → Whole Class
• 4 activities

Activity 01

• Experiential Learning
• 25 min · Pairs

Pairs Task: Finding Center of Gravity

Provide irregular cardboard shapes to pairs. Students balance each on a pivot point or suspend from strings to mark the center of gravity. They then tilt the shapes slightly and note if the line of action stays within the base.

Explain how the position of the center of gravity affects the stability of a racing car.

Facilitation Tip

During the Pairs Task, circulate to ensure students alternate roles between holding and balancing so both practice the suspension method.

What to look for

Provide students with several irregular flat objects (e.g., a cardboard cutout of a car, a ruler). Ask them to use the suspension method to find and mark the center of gravity for each. Observe their technique and accuracy.

• Apply
• Analyze
• Evaluate
• Self-Awareness
• Self-Management
• Social Awareness

Activity 02

• Experiential Learning
• 40 min · Small Groups

Small Groups: Stability Testing

Groups receive stackable blocks with adjustable masses. They test toppling angles for different center of gravity heights and base widths, recording data in tables. Compare results to predict stable configurations.

Predict whether an object will topple based on its center of gravity and base of support.

Facilitation Tip

In Stability Testing, ask groups to sketch their objects' centers of gravity before testing to build visual prediction skills.

What to look for

Present students with images of a tall, narrow vase and a wide, flat-bottomed jug. Ask: 'Which object is more stable? Explain your reasoning using the terms center of gravity and base of support. How could you make the vase more stable?'

• Apply
• Analyze
• Evaluate
• Self-Awareness
• Self-Management
• Social Awareness

Activity 03

• Experiential Learning
• 45 min · Small Groups

Whole Class: Racing Car Stability Challenge

Display toy cars on ramps. Class predicts toppling as weights shift the center of gravity. Groups then modify their cars and test on curved tracks, sharing designs that succeed.

Design an object with enhanced stability by manipulating its center of gravity.

Facilitation Tip

For the Racing Car Challenge, provide masking tape to mark bases and encourage precise measurements to connect geometry with stability.

What to look for

Give students a scenario: 'A toy truck is loaded with blocks. If the blocks are stacked high, is the truck more or less stable? Justify your answer by referring to the truck's center of gravity and base of support.'

• Apply
• Analyze
• Evaluate
• Self-Awareness
• Self-Management
• Social Awareness

Activity 04

• Experiential Learning
• 30 min · Individual

Individual: Design a Stable Object

Students sketch and build a freestanding model with low center of gravity and wide base using craft materials. Test by nudging gently and refine based on observations.

Explain how the position of the center of gravity affects the stability of a racing car.

What to look for

Provide students with several irregular flat objects (e.g., a cardboard cutout of a car, a ruler). Ask them to use the suspension method to find and mark the center of gravity for each. Observe their technique and accuracy.

• Apply
• Analyze
• Evaluate
• Self-Awareness
• Self-Management
• Social Awareness

A few notes on teaching this unit

Teach this topic by starting with hands-on discovery, then guiding students to generalize principles from their observations. Avoid rushing to formulas; let students experience the physical relationships first. Research shows that tactile experiences strengthen spatial reasoning in physics, especially for students who struggle with abstract diagrams.

Successful learning looks like students accurately locating centers of gravity, explaining stability using both center of gravity and base of support, and applying these ideas to real-world designs like racing cars. They should confidently predict toppling by analyzing object shapes and loading conditions.

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Watch Out for These Misconceptions

• During Pairs Task: Finding Center of Gravity, watch for students assuming the center is always halfway across an object.

  Direct students to mark the point where the object balances on a knife edge, then compare this to the geometric center to highlight the difference in irregular shapes.

• During Stability Testing, watch for students attributing stability solely to low center of gravity.

  Have groups compare two bases of the same height but different widths, showing how base size affects stability even when centers are equal.

• During Racing Car Stability Challenge, watch for students believing stability depends only on speed.

  Ask students to tilt their car models manually to observe toppling without external pushes, reinforcing the role of center of gravity relative to the base.

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Methods used in this brief

• Experiential Learning