Supplies:

• 1 Mouse trap (rat traps are even better!)
• Toy wheels (either with small tacks/nails or on axles) - up to 4
• string
• elastics
• Elmer's glue
• odds and ends (toothpicks, small sticks, thread spools, small blocks, etc.)  

Procedure:

A short presentation is given about basic physics, including momentum, mechanical  advantage and friction.

Students work in teams of 2-4 to develop a mouse trap car. The car is to be propelled  by the mousetrap only (no external propulsion sources). The parts may be used in any  fashion desired. When complete, there are race trials of the vehicles. Prizes are given  for the longest distance traveled.

Extensions:

Cars could be weight limited.

Races could be in categories - time trials over a set distance, longest distance,  fastest acceleration, best  weight/distance ratio.

Students advancing to the next round can optimize their cars and make adjustments.

Notes:

Leader may mention that the car can coast after the trap has expended its energy (this  is  sometimes not obvious.)

The elastics are great for tire treads as the plastic wheels slip on smooth floors when  the trap closes. Some groups will discover this as they test their cars. Heavy cars work  best as they  allow for smooth acceleration and great momentum over the distance.

Thanks to Joel Morrissette at Folsom for providing this activity idea.