Activity 01
Small Groups: CoG Balancing Stations
Prepare stations with irregular cardboard shapes, string, and retort stands. Groups suspend each shape from two points to find balance lines, intersecting at the CoG. They sketch and label findings, then test by placing CoG over a pivot.
Explain how the position of the centre of gravity affects the stability of a racing car.
Facilitation TipDuring CoG Balancing Stations, circulate to ensure students suspend shapes from varied points and trace plumb lines carefully before marking intersections.
What to look forProvide students with several irregular shapes made of cardboard. Ask them to suspend each shape from at least two different points and draw lines along the plumb bob. The intersection of these lines is the CoG. Have them mark it and predict which shape is most stable based on its CoG position relative to its base.
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Activity 02
Pairs: Tilt Stability Challenge
Pairs construct paper models varying base width and CoG height using clay weights. They tilt each on a protractor board, record tipping angles, and graph results to compare stability factors. Discuss which design wins.
Design an object with maximum stability given its shape and material distribution.
Facilitation TipFor the Tilt Stability Challenge, remind pairs to measure tilt angles consistently using a protractor or marked reference line on the table.
What to look forPresent images of a double-decker bus and a sports car. Ask: 'How does the placement of the engine and passengers affect the stability of each vehicle? Which vehicle is more likely to tip over on a sharp turn, and why? Use the terms 'centre of gravity' and 'base of support' in your explanation.'
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Activity 03
Small Groups: Racing Car Stability Build
Provide cardstock, wheels, and weights. Groups design low-CoG cars, test on curved ramps for tipping, adjust mass distribution, and retest. Class shares data on optimal designs via whiteboard.
Evaluate how a change in the base area affects the stability of a structure.
Facilitation TipIn Racing Car Stability Build, provide a range of materials and challenge groups to justify their design choices in writing before testing.
What to look forGive students a scenario: 'A builder is designing a temporary stage for a concert. What two design considerations related to the stage's base and weight distribution would you recommend to maximize its stability?' Students write their recommendations and a brief justification.
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Activity 04
Whole Class: Base Area Demo
Demonstrate blocks with varying bases tilted together. Class predicts and observes tipping order, then pairs replicate with foam shapes, measuring base effects quantitatively.
Explain how the position of the centre of gravity affects the stability of a racing car.
Facilitation TipFor the Base Area Demo, use a light source to project the CoG’s vertical line onto the base, making the concept visible for the whole class.
What to look forProvide students with several irregular shapes made of cardboard. Ask them to suspend each shape from at least two different points and draw lines along the plumb bob. The intersection of these lines is the CoG. Have them mark it and predict which shape is most stable based on its CoG position relative to its base.
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Generate Complete Lesson→A few notes on teaching this unit
Teach this topic through iterative testing: start with simple shapes to establish the concept of CoG, then introduce irregular objects to challenge assumptions. Avoid relying solely on diagrams, as students benefit from the kinesthetic experience of balancing and tilting. Research shows that students who physically manipulate objects develop stronger spatial reasoning and retain ideas longer.
Students will confidently locate the centre of gravity for irregular shapes, explain how base width and CoG height affect stability, and apply these principles to design stable structures. Their explanations should reference empirical evidence from their balancing and tilting activities.
Watch Out for These Misconceptions
During CoG Balancing Stations, watch for students assuming the CoG is always in the middle of an oddly shaped object.
Have them suspend an irregular cardboard shape from two points, trace the plumb lines, and mark the intersection. Point out how the lines converge away from the geometric centre, using peer comparisons to reinforce the empirical method.
During Tilt Stability Challenge, watch for students attributing stability only to the object’s height.
Ask them to compare the tilt angles of a tall, narrow cylinder and a short, wide cylinder. Have them measure and record when each topples, then discuss how base width contributes to stability alongside CoG height.
During Racing Car Stability Build, watch for students believing a lower CoG makes balancing harder.
Direct them to add weights to lower or raise the CoG in their car models, then tilt the platform incrementally. Ask them to observe which configuration resists tipping more easily and record their findings in a quick group discussion.
Methods used in this brief