Mullet wheels wedding

Ideas for physics project!!! PLZ help!? - mini sand car blue prints

We must build a mini-car, without making use of electrical equipment or chemicals, progress ... The device has a mechanical energy and Šrot EVR wat is used to converge these forms of energy must be traveling by car (ie give a mouse trap set in his car and left his addition, which will increase as the car door on the ground repels). ... I did not travel and only 0.5 m over a smooth surface! his alleged trip on a length of 1.2 m, with different floors (carpet, 1cm of water, sand, etc. ..) no idea that the case? o How can I ensure the more efficient the trap? (ie, wat to use for wheels? mass?) thnks!