1. MESA Day 2013 Mousetrap Car 6th-8th Grade - Distance
9th-12th Grade - Accuracy

2. Objective & Materials
Students will build a vehicle solely powered by a standard mousetrap to travel the longest distance on a specified track (MS) or stop the closest to a specified target (HS).
Materials:
1 standard mousetrap
All other materials are legal
NO KITS!

3. First Things First: READ RULES AT LEAST TWICE!!
Mousetrap is ONLY source of energy
Don’t tamper with mousetrap:
No paint
No decoration
Alteration allowed ONLY for attaching mousetrap to chassis
Spring may not be altered

4. Let’s review physics! Energy: It’s what moves the car.
Potential: energy stored in a system (mousetrap spring)
Elastic & Gravitational
Kinetic: energy of motion
Potential  Kinetic
Inertia: The resistance an object has to changing its state of motion.
Rotational Inertia: The resistance an object has to changing its state of rotation.
Friction: A force that opposes the direction of motion.
Static: caused from two surfaces pressing together.
Fluid: caused from liquids or gases. In air, this is known as drag.
Torque: The force required to rotate an object.
Power: The rate at which energy is released or transformed in a system.

5. The Engine: Spring + Lever Arm
Energy from spring is transferred to car via the lever arm
Lever arm provides torque required to turn axles
Length of lever arm affects power output
Shorter arm = faster output
Longer arm = slower output

6. Wheels & Axles # of wheels : 3 or 4 Wheel radius Wheel grip (traction)
The greater the radius, the greater the torque required to rotate the axle
Wheel grip (traction)
Power output must match wheel grip to avoid spinning
Avoid wasting energy
Ratio of wheel-to-axle
Larger ratio good for distance, but not necessarily for accuracy
Friction
Reduce friction between wheels and surface
Also between axle and chassis
Alignment

7. Wheels & Axles

8. The Chassis The body of the car
Balsawood, plastic, other lightweight materials
Mass
The heavier the car, the greater the friction force with the surface
More force required to actually move the car
Long chassis vs. Short chassis
Narrow vs Wide
Aerodynamics (negligible)

9. Fast vs Slow
Fast:
Build a car that will accelerate quickly and “coast” as far as possible
shorter lever arm
smaller wheel radius
quick power output
Slow:
Build a car that will accelerate slowly over the entire distance that it travels. Less “coasting”.
longer lever arm
larger wheel radius
slow power output
Accuracy:
Can be fast or slow
Length of lever arm
Wheel and axle size
Braking mechanism?
quick power output

10. Tips for avoiding DQ’s:
Research, research, research!
Experimentation is the key
Set a working timeline
READ THE RULES….twice….again!!
HAVE FUN!!!: It’s not the end of the world.

11. Remind Students: Research, research, research!
Experimentation is the key
Set a working timeline
READ THE RULES….twice….again!!
HAVE FUN!!!: It’s not the end of the world.

12. Let’s Build… Marvin Maldonado Director, SDSU MESA