Early Simple Machines Set

Crossing Crocodile River

Applying knowledge and skills related to structures, stability, measuring, and fair testing.

30-45 min.
Years 1-2

The Problem

(5-10 Minutes)

Sam and Sara are on a jungle hike when they come to a fast-fl owing river. They can see several crocodiles swimming in the river. Sam and Sara need to cross the river.

Can you help Sam and Sara get across the river safely?


Design Brief

(3-5 Minutes)

Design and make a safe and strong bridge that:

  • is at least 20 cm long without touching the water
  • is at least 10 cm above the water
  • supports the weight of at least Sam and Sara

Fair Testing and Fun

(10-15 Minutes)

  • Is the bridge 20 cm long or even longer?
    Measure with a ruler or with the LEGO® DUPLO® box lid, which is 27 cm wide. The longer, the better.

  • Is it at least 10 cm above the water?
    Measure it and see.

  • Is it safe?
    Take the Sam and Sara models for a walk across the bridge.
    Can Sam and Sara walk on the bridge at any place without falling through holes or gaps?

  • How much weight can it carry?
    *Where might the weakest place be? In the middle! Start with Sam in the middle, add Sara.

Still OK? Then keep adding more weight (e.g. bricks) until it breaks! The more weight it can carry, the stronger the bridge.*


Extra Challenge

(10-15 Minutes)

Design a boat that can go under your bridge and sail down the river.

Teacher Support

To be able to apply knowledge and skills relating to:
The application of fair testing and product safety

9656 Early Simple Machines Set (one set per two students is recommended)