How to make a gravity driven vehicle?

Question

The vehicle has to be made just as a working prototype to run for short distance on a flat surface, which has to powered only by gravity and nothing sort of spring rubber band, string etc

Answer 1

Attach a heavy weight to a pulley and use gear box to distribute potential energy to wheels.

Answer 2

The easiest way I can think of - only one moving part - is to place a tube at about 45 degrees extending up from the middle of the vehicle. Put a hard stop on the front end of the tube connected firmly to the vehicle and simply drop a heavy ball into the tube. When the ball rolls down the tube and slams into the stop, the kinetic energy will propel the car forward. The heavier the ball and/or the longer the tube (within reason:) the further the vehicle will travel.
You can experiment with different angles of the tube to see which one gives the vehicle the greatest forward momemtum on a level surface - 45 degrees is mathematically desired for maximum thrust at 180 degrees (level). The ball should exit the tube, perhaps a nice smooth curve in the bottom of the tube toward the front of the vehicle, and strike the stop at the same angle as the level surface for maximum forward thrust.
Have fun!

Answer 3

One method is to make the axle for the drive wheels a larger cylinder, like a sewing bobbin. On the vehicle a post and bar mount a pulley in the air. A string is wound on the cylinder, through the pulley and hooked to a weight. When the weight is released, it pulls the string which drives the cylinder, which turns the wheels which drives the vehicle.

Answer 4

Expanding on what Leann said, use a curved tube so that when the ball hits the stop its velocity is horizontal.

Answer 5

Get a soap box. Add wheels. Put it at the top of a hill.