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

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!

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

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.

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

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

Wheels & Axles

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)

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

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.

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.

Let’s Build… Marvin Maldonado Director, SDSU MESA mmaldonado@projects.sdsu.edu