When talking about "How do ants take the shortest way", the teacher can use the ready-made rectangular model of the chalk box to spread the chalk box in three different directions to get three different walking modes, then compare the sizes of the three distances after calculation, and finally get the shortest distance.

2, inclinometer production:

The protractor changes from 90 degrees to 0 degrees, from 0 degrees, the left and right sides increase in turn, until 180 degrees on both sides becomes 90 degrees; Fix the protractor upside down on the horizontal line at the top of the T-frame, so that the diameter of the protractor is horizontal when the T-frame is vertical to the ground; Hang a rope with a key in the center of the circle.