This model is a working model and you should read this if you are searching for a quick maths model to make. Its related to trigonometry. The name of this device is theodolite.A theodolite is an instrument used for determining the horizontal and vertical angles between two points.
Piece of wood or cardboard wider than the protractor
Push pin or nail
1. Align the center of the flat edge of the protractor with the centre of the
long edge of the wood or cardboard.
2. Firmly attach the protractor to the wood or cardboard using the push pin
or nail. Push the push pin or nail in by hand or use a hammer.
3. Avoid breaking the protractor or shifting it out of position.
4. Attach the weight to one end of the string. Attach the other end of the
string to the push pin or nail.
hope i helped u:)