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Directions: Fill in the bright yellow (required). Calculate the green or override with what you think is the best answer. Blue is optional. The "stats" should automatically populate, except for the frame length (which you enter) and the actual acceleration distance and velocity.Car Stats
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Rubber Band Car Analysis and PredictionsDrive wheel radius (m)Other wheel radius (m)Overall Mass (kg)Band Stretch Distance (m)Frame length (m)Maximum Rubber Band Tension (N)Motor Input Energy (J)Overall Estimated Efficiency (%)Predicted Acceleration Distance (m)Predicted Maximum Velocity (m/s)Actual Acceleration distance (m)Actual Max Velocity (m/s)Sum of fractional errorsOverall Contest Score
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Problem #Quantity measuredValueProblem #Quantity measuredValue0.080.060.270.12160.972%2.41.682.500.920.860.12
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1Max Static Friction (N)0.810Drive Axle Friction Torque (Nm)0.0008
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2Rotations10Angular displacement of drive axle during accel (rad)30
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String Length (m)0.27Drive Axle Friction Energy Loss (J)0.024
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Axle Radius (m)0.004297183463Front Axle Friction Torque (Nm)0.0005
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3Drive wheel Radius (m)0.08Linear distance traveled by car during acceleration (m)2.4
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Drive axle radius (m)0.004Front wheel radius (m)0.06
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Max String Tension Without Slipping (N)16Angular displacement of front axle during accel (rad)40
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4Max Rubber Band Tension (N)15Front Axle Friction Energy Loss (J)0.02
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Stretch distance (m)0.12Sum of Front and Back Energy Losses to Friction (J)0.044
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5Length of string that will unwrap0.12Additional energy loss due to friction, based on your intuition? (J)0.01
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Drive axle radius (m)0.004Total Energy Loss Due To Friction (J)0.054
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Angular displacement of drive wheels (rad)3011Car Total Mass (kg)0.27
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Linear distance traveled by car during acceleration (m)2.4Total Energy Provided By Motor (J)0.7056
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6k (N/m)125Total Energy Lost To Friction (J)0.054
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Energy Input (J)0.9Total KE of Car after Acceleration (J)0.6516
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7Mass (kg)0.6Drive Axle I (kgm^2)0.0007
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Height gained (m)0.12Front Axle I (kgm^2)0.0003
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Motor output Energy -- based on the numbers above or your own method (J)0.7056Drive Wheel Radius (m)0.08
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8Efficiency (%)78%Front wheel radius (m)0.06
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9Use your wheel and axle moment of inertia spreadsheet and use the data in steps 10 and 11.Max Car Velocity (m/s)1.678231526
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Wheel and Axle Calculator for Frictional Torque and Moment of Inertia
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Item to measure or calculateFormula Performing Calculation
No units here!!!
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Axle Radius (m)0.005
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Mass of falling weight (kg)0.1
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Wrapped String length (m)0.7
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Acceleration time (s)5
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Deceleration time (s)25
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Falling Weight acceleration during string pull -- absolute value (m/s/s)0.056
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Wheel and axle angular acceleration during string pull -- absolute value (rad/s/s)11.2
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String tension during string pull (N)0.9744
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Torque applied by string during fall -- absolute value (Nm)0.004872
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Max angular speed of wheel and axle (rad/s)56
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Angular acceleration of wheel and axle during slowing period -- absolute value (rad/s/s)2.24
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Wheel and Axle Moment of Inertia (kgm^2)
0.0003625
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Torque due to friction -- absolute value (Nm)0.000812
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