Biomechanics of throwing a frisbee Daniel Kim Biology

Biomechanics of throwing a frisbee Daniel Kim Biology 438 -301 Professor Rome

Once upon a time… �Wham-O Toys �Bridgeport, CT – William Russell Frisbie opened Frisbie’s Pie Company

Frisbee Throws �Backhand �Standard �Skipping �Hover �Curve Pass �Forehand �Overhead �All work under a similar principle

3 Stages of a Frisbee Throw �Wind-up �Acceleration �Follow through

The Backhand Throw

Backhand Throw

Wind Up (backhand) �Torso twists (winding up) �Weight of thrower shifts to left foot �Arm horizontally adducts towards torso �Forearm flexes �Wrist curls

Acceleration �Continues from maximum rotation of torso �Sequential uncoiling of torso and arm �Torso twists right and bends forward �Weight shifts to right foot �Humerus and torso are aligned �Forearm pronates �All-important wrist flick

Follow Through �Arm continues to extend at shoulder, elbow, and wrist �Finished when torso twists maximally to the right

Second Look at the Backhand

Second Look at the Backhand

X-Displacement vs. Time

Force Generated and Work Performed � Assuming that mass of a human arm is about 6. 5% of total body weight: �marm= 73 kg*. 065 = 4. 75 kg � Acceleration prior to release was 22. 65 m/s^2 � Force = Mass * Acceleration � 4. 75 kg * 22. 65 m/s^2 = 107. 6 N � Work = Force * Distance �Distance traveled: 1. 412 m � 107. 6 N * 1. 412 m = 152 J � Velocity from logger pro (calculated in quadrature): 13. 1 m/s

The Forehand Throw

Forehand Throw

Wind Up �Feet facing receiver �Knees slightly bent �Weight shifted to right foot �Torso turns right (winding up) �Shoulder horizontally abducts away from torso �Elbow pointing forward

Acceleration and Follow Through �Torso unwinds �Shoulders rotate giving speed �Elbows straighten �Wrist snaps �Throw completed when torso is facing forward

Second Look at the Forearm Throw

Second Look at the Forearm Throw

X-Displacement vs. Time

Force Generated and Work Performed � Assuming that mass of a human arm is about 6. 5% of total body weight: �marm= 73 kg*. 065 = 4. 75 kg � Acceleration prior to release was 23. 97 m/s^2 � Force = Mass * Acceleration 4. 75 kg * 23. 97 m/s^2 = 114 N � Work = Force * Distance �Distance traveled: . 8594 m � 114 N *. 8594 m = 100. 0 J � Velocity from logger pro (calculated in quadrature): 12. 3 m/s

Conclusions �Compare energy inputted to the velocity of the frisbee to see which throw is more energy efficient �Backhand Throw: � 152 J / 13. 1 m/s = 11. 60 �Forehand Throw: � 100 J / 12. 3 m/s = 8. 13 Given this single trial, the backhand form requires more energy than the forehand form.

Future Investigation �Using different camera angles, calculate the energy inputted as rotational energy. Which throw puts more spin into the frisbee? �Investigate the specific backhand throws (skipping, hover, curve pass) and analyze how the body inputs the proper energy to manipulate the trajectory of the frisbee.

Resources �http: //morleyfielddgc. files. wordpress. com/2009/04 /hummelthesis. pdf