At the start of the lesson, with the playground empty, Year 5 chalk a 1 m square in one corner and rule it into one hundred 10 cm squares. The class stands behind a school tablet on a tripod, framed on the grid alone with a running stopwatch laid beside it, and the teacher tips a litre of water onto the middle while the tablet films in slow motion. The water reaches its full spread in about three seconds, far too quickly to count anything. Back inside, the teacher plays the clip on the board and pauses each time the stopwatch in the picture shows another half second. At each pause children count the squares that are half or more wet, the method they use for irregular shapes in the textbook, and record an estimate: 5 squares at half a second, then 14, 26, 35, 40 and 42 at three seconds, which is 4,200 cm² because each square is 10 cm by 10 cm. They plot the six estimates as a line graph in their books and describe how the area grows quickly and then levels off.
Tools: Built-in camera (slow motion and time-lapse) Nine ideas for your own version in Generate
This page is one of a growing set of PICRAT examples by cell, subject and grade. Page maintained by Andy Perryer.