Choose one task, model or clip within the current lesson stage. These resources support the existing two separate 40-minute lessons; they do not add another lesson or extra time.
Week 4 · Tuesday: Move the pivot, compare the effort
Name: ____________________ Date: ______________
We Do · think together
Predict a gear pair
Two meshing gears have 20 and 40 teeth. The 40-tooth gear makes one complete turn.
The gear calculation uses an ideal model. Only record a lever observation if the comparison actually happened; do not invent force measurements.
- How many turns must the 20-tooth gear make?
- Do meshing gears turn in the same or opposite directions?
- What does this model leave out?
Discuss, point, draw, write or dictate a first explanation. Choose one example first; extend only if there is time.
Reveal a worked explanation after an attempt
The 20-tooth gear makes two turns in the opposite direction: 40 teeth pass the contact point. This ideal model leaves out friction and deformation. It does not mean the smaller gear supplies both more speed and more turning force.
Give a smaller support cue
Use: “The pivot is closer to … . I noticed … . For the same lift, the hand moves …”.
Writing stays in this open page only. It is not saved or sent. Copy any record you want to keep before leaving.
Apply it
Use the current workshop
Compare the two prepared lever positions, or explain them from the diagram. Record the same load, the pivot position and the observed effort. Explain the gain and the cost.
Teacher model · compare with the pupil’s evidence
With the pivot nearer the load and a longer effort arm, less effort is needed for the same load, but the effort point travels farther for the same load rise. A diagram explanation is modelling; only record observations if a comparison was actually made.