MESA Mouse Trap Powered Cars

Basic Competition Rules Greatest distance travelled without leaving 6-foot wide track Zero alteration of mousetrap do not take the spring apart do not drill holes in or paint the trap except screw attachment holes trap lock must be working and sprung with a pencil or similar object

Basic Car Design

Advanced Car Design

Physics of Mousetrap Car Friction forces Drag Acceleration Torque Momentum

Friction Rubbing forces on moving parts Effect: slows car and prevents maximum distance Caused by: excess wheel to road contact poor wheel alignment various parts rubbing when in motion

Wheel to road contact Skinny wheels incur less friction than wide wheels “total surface area” of all wheels

Skinny Wheels Skinny Wheels work best

Poor Wheel Alignment Axles should be aligned perpendicular to car; if not, Cars veers to right of left Excess friction between front and back axles

Moving parts rubbing Axles rubbing on car body Axles rubbing on mounting screws or holes Lever arm against body String against body or axle Wheels against body

Drag Anything that slows or stops the car Such as: Friction Parts hanging off car Wide lever arm or wheels

Acceleration Getting the car moving with trap Strongest possible residual strength in mouse trap Optimum lever-arm to car length ratio (also consider trap position) Too long or short of lever arm reduces potential acceleration Friction reduces acceleration

Torque Getting power to the wheels: ability to get car moving Too much torque = less distance (wheel spin) Too little torque = car will not move Torque altered by changing power arm angle to axle Firm string to axle attachment

Momentum Keeping the car moving after acceleration phase less friction = greater distance the heavier the car, the greater the momentum

Long vs Short Car Long Cars: less torque less speed less momentum much longer acceleration period Short Cars: more torque greater speed more momentum shorter acceleration period

Long Car

Short Car

Maximizing distance longest power arc (arm length) ideal torque (mousetrap position) largest wheel diameter (greatest distance per wheel revolution) smallest axle diameter (most revolutions per inch of string)

Long Arm 2009

Large Wheel Diameter

Large Diameter wheels Small Diameter Axles

Comes Down to Car with trap not modified least amount of friction maximizes design acceleration capability finds ideal torque for design most possible momentum stays on the track

Summary: Building Tips Large drive wheels Small drive axle Do not tie string to axle Axles perpendicular to car Correct mouse trap relation to car length

Connecting arm to trap

Tip: Don’t tie string to axle

For More Info….

2002

Attaching axle to car

drrusshill@gmail.com The End