The room is the data.

• One pendulum, everybody's stopwatch

  A classroom experiment with three trials per timing method, on a pendulum the big screen draws, with a period the lesson knows, or on a real one in the room. Students time on their phones, or type a reading, and submit raw elapsed readings, units and actual cycle counts; Decka compares complete pairs one trial at a time and draws the screen pendulum's known period beside them. Does the spread change? Missing readings stay missing, and a tighter spread does not prove greater accuracy.

  Up to 600 people

  Measurement and uncertaintyRepeated measurement

  PlayingHow it plays, and how to run it
• How many table-tennis balls would fill this room?

  Nobody knows, nobody is meant to know, and there is nothing to look up — you break it into a room you can see and a ball you can picture, and divide. Everybody answers as a power of ten and says how sure they are. The board shows the room's spread, overall and split by how sure people said they were, before a worked example checks the reasoning. Whether the surest agreed more closely, and whether agreeing made anyone right, is the debrief. An estimate you would not defend is still worth having, as long as you say which one it is.

  Up to 600 people · About 13 min

  Order-of-magnitude estimationCollective estimation

  Try itHow it plays, and how to run it
• A lorry and a car meet head-on

  A forty-tonne lorry meets a small car head-on. Which one pushes harder on the other? The room votes alone and is shown how its votes fell, argues it out with someone who chose differently, and votes again — with the first board taken down and nobody having been told the answer in between. The second board is marked and the first one is not, so the debrief can ask what changed between the votes, and which argument did it.

  Up to 600 people · About 7 min · 2 acts

  Newton's third lawForce and acceleration

  Try itHow it plays, and how to run it

Every activity here ships with Decka — sign up free and add any of them to your library from the built-in classroom catalog.