Gather a mousetrap, lightweight chassis material, 4 wheels, 2 axles, string, glue, tape, and tools
Build a straight, rigid chassis
Mount the mousetrap securely on the chassis
Attach axle supports so the axles spin freely
Insert the front and rear axles
Attach wheels firmly to both axles
Make one drive axle longer if needed for string wrapping
Tie one end of the string to the mousetrap arm
Wrap the string around the drive axle
Pull the mousetrap arm back and secure the string on the axle
Set the car on a smooth surface
Release the mousetrap arm to drive the car
Adjust wheel alignment if the car veers
Reduce friction in axles and wheel contact points
Use larger drive wheels or a longer lever arm for more distance
Use lighter materials to improve performance
Test repeatedly and refine the design