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Leaning tower

  • Key Stage 3
  • Topical

Type: Activity
Learning Strategy: Case study
Topic: Forces

The Leaning Tower of Pisa has finally been stabilised from its dangerous leaning position. Students imagine they were the part of the engineering team, coming up with solutions to stop it leaning. Through this context, students explore the science of stationary stable structures.

The lesson makes use of ‘Sodaconstructor’ a software tool for experimenting with and building structures that can move, and even race against each other.

Published: 23rd June 2008
Reviews & Comments: 0

Learning objectives

Students will:
• Understand the idea of centre of mass
• Understand that a force can make an object topple over (turn about a pivot)
• Understand that for a stable structure, a line drawn perpendicularly down from the centre of mass must lie inside the envelope of the ‘base’ i.e. the supporting legs.
• Investigate the stability of structures and how to stabilise unstable structures with, for example, cantilevers

Try the activity

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11-14 (KS3)

1.1a Using scientific ideas to explain phenomena, and developing them creatively to generate and test theories (ideas about stability to explain why simple Soda models stay up – or not; or predictions related to centre of gravity)

3.1b Forces are interactions between objects and can affect their shape and motion

Running the activity

Slide 1 - Starter
This puts students in the role of construction engineers working out how to help the citizens of Pisa.

Slide 2 – Modelling the leaning tower
Do this as a demo or practical (see below). For older students this could just be a thought experiment to give more time for the computer modelling activities.

To model the leaning tower of Pisa, use:
- clay from the art department
- a section of plastic drainpipe or plastic 10cm sewer pipe (unused!), approx 40 cm long

Fill a lab equipment tray with sand to act as the ‘earth’ and tamp it down well to make a firm base. Push one side of the pipe more and more into the ‘earth’ to simulate the tilt, until you eventually get a topple. Record the angle. Elicit that if a line drawn perpendicularly down from the centre of mass lies inside the envelope of the ‘base’ i.e. the supporting legs, a structure is stable. If the perpendicular line from the centre of mass is outside the base, then the structure will topple.

Slide 3 - modelling stability with ‘Soda’ software
Students explore the concept of stability using a simple software model. Engineers use software to model their solutions before working with real materials. The web link below for the 'tower' opens a program called ‘soda constructor’

Pick up the right corner (black dot) of the ‘tower’ with the mouse. Pull it further to the right to tilt the tower. Let go and see if it returns to the original position – if it does, it’s stable. Try again but move the black dot further to the right. Demonstrate the stability rule that as soon the centre of mass (the point of intersection of the diagonals) goes beyond the base, the tower falls over. There is no need to move the sliders (gravity, friction and springiness on the right of the screen.

Slide 4 - investigating solutions
Investigate a range of methods to stabilise the tower near its toppling point, for example
• fixing a heavy mass in the base
• excavating ‘earth’ from under the opposite side to the tilt
• attaching a guy rope (string) to prevent topple
• adding mass to the ‘masonry’ on the opposite side of the tower to the lean
• using a cantilever

Students record their results on slide 6 (printed out as a worksheet).

Slide 5 - Plenary
Show students the news report. How did the engineers actually stabilise the tower? How did the students’ solutions compare?

News links

The leaning tower news story
BBC news story about stabilizing the Leaning Tower of Pisa
Leaning tower of Pisa
Find out about the history of the tower.
Sodarace is the online olympics pitting human creativity against machine learning in a competition to design robots that race over 2D terrains using the Sodaconstructor virtual construction kit
Computer Science for Fun
A site from one of the developers of SodaRace, on the fun side of computer science - about people, solving puzzles, creativity, changing the future.

Media links

The tower model
A simple software model to manipulate to explore the concept of stability. The web link opens a program called 'soda constructor'.
Daintywalker model
Try the 'Daintywalker model' and click 'run' to see it move.

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