mesa mouse trap powered cars. basic competition rules greatest distance travelled without leaving...
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MESAMESAMouse Trap Powered CarsMouse Trap Powered Cars
Basic Competition RulesBasic Competition RulesGreatest distance travelled Greatest distance travelled without leaving 6-foot wide trackwithout leaving 6-foot wide trackZero alteration of mousetrapZero alteration of mousetrap– do not take the spring apartdo not take the spring apart– do not drill holes in or paint the do not drill holes in or paint the
traptrapexcept screw attachment holesexcept screw attachment holes
– trap lock must be working and trap lock must be working and sprung with a pencil or similar sprung with a pencil or similar objectobject
Basic Car DesignBasic Car Design
Advanced Car Design
Physics of Mousetrap CarPhysics of Mousetrap CarFriction forcesFriction forces
DragDrag
AccelerationAcceleration
TorqueTorque
MomentumMomentum
FrictionFrictionRubbing forces on moving partsRubbing forces on moving partsEffect: slows car and prevents Effect: slows car and prevents maximum distancemaximum distanceCaused by:Caused by:– excess wheel to road contactexcess wheel to road contact– poor wheel alignmentpoor wheel alignment– various parts rubbing when in various parts rubbing when in
motionmotion
Wheel to road contactWheel to road contactSkinny wheels incur less Skinny wheels incur less friction than wide wheelsfriction than wide wheels
““total surface area” of all total surface area” of all wheelswheels
Skinny Wheels Skinny Wheels Skinny Wheels work best
Poor Wheel AlignmentPoor Wheel AlignmentAxles should be aligned Axles should be aligned perpendicular to car; if not, perpendicular to car; if not,
Cars veers to right of leftCars veers to right of left
Excess friction between front Excess friction between front and back axlesand back axles
Moving parts rubbingMoving parts rubbingAxles rubbing on car bodyAxles rubbing on car body
Axles rubbing on mounting Axles rubbing on mounting screws or holesscrews or holes
Lever arm against bodyLever arm against body
String against body or axleString against body or axle
Wheels against bodyWheels against body
DragDragAnything that slows or stops Anything that slows or stops the carthe car
Such as:Such as:
FrictionFriction
Parts hanging off carParts hanging off car
Wide lever arm or wheelsWide lever arm or wheels
AccelerationAccelerationGetting the car moving with trapGetting the car moving with trap
Strongest possible residual Strongest possible residual strength in mouse trapstrength in mouse trap
Optimum lever-arm to car length Optimum lever-arm to car length ratio (also consider trap position)ratio (also consider trap position)
Too long or short of lever arm Too long or short of lever arm reduces potential accelerationreduces potential acceleration
Friction reduces accelerationFriction reduces acceleration
TorqueTorque Getting power to the wheels: Getting power to the wheels: ability to get car movingability to get car moving Too much torque = Too much torque = less less distance (wheel spin)distance (wheel spin) Too little torque = car will not Too little torque = car will not
movemove Torque altered by changing Torque altered by changing power arm angle to axlepower arm angle to axle Firm string to axle attachment Firm string to axle attachment
MomentumMomentum Keeping the car moving after Keeping the car moving after
acceleration phaseacceleration phase
less friction = greater less friction = greater distancedistance
the heavier the car, the the heavier the car, the greater the momentumgreater the momentum
Long vs Short CarLong vs Short Car Long Cars:Long Cars:
less torqueless torque
less speedless speed
less less momentummomentum
much longer much longer acceleration acceleration periodperiod
Short Cars:Short Cars:
more torquemore torque
greater speedgreater speed
more more momentummomentum
shorter shorter acceleration acceleration periodperiod
Long Car
Short Car
Maximizing distanceMaximizing distance longest power arc longest power arc (arm length)(arm length)
ideal torque ideal torque
(mousetrap position)(mousetrap position)
largest wheel diameter largest wheel diameter (greatest distance per (greatest distance per wheel revolution)wheel revolution)
smallest axle diameter (most smallest axle diameter (most revolutions per inch of string)revolutions per inch of string)
2009
Long Arm
Large Wheel Diameter
Large Diameter wheels
Small Diameter Axles
Comes Down to Car withComes Down to Car with
trap not modified trap not modified
least amount of frictionleast amount of friction
maximizes design maximizes design acceleration capabilityacceleration capability
finds ideal torque for designfinds ideal torque for design
most possible momentummost possible momentum
stays on the trackstays on the track
Summary: Building TipsSummary: Building Tips
Large drive wheelsLarge drive wheels
Small drive axleSmall drive axle
Do not tie string to axleDo not tie string to axle
Axles perpendicular to carAxles perpendicular to car
Correct mouse trap relation Correct mouse trap relation to car lengthto car length
Connecting arm to trapConnecting arm to trap
Tip: Don’t tie string to axle
For More Info….
2002
Attaching axle to car
The End The End