WHY DO BOOMERANGS COME BACK? Yutaka Nishiyama ...

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344 Y. Nishiyama Figure 8: The plane of rotation changes direction if couple is applied from the top and bottom Figure 10: Right-hand rule Figure 9: The plane of rotation becomes horizontal when couple is applied from the front and back
WHY DO BOOMERANGS COME BACK? 345 photocopies. Trace this on an advance copy (using a cardboard with thickness between 0.5 to 0.7 mm) and cut it out neatly using scissors. Put a sign or note saying front so as not to mistake the front and back sides. It is particularly important to keep the difference between the front and back sides in mind. Place a ruler along the dotted line and indent the line deeply three or four times using a ballpoint pen. This is done to make it easy to bend or turn along these lines. Figure 11: Swept-back wing boomerang With the front side faced upward, make mountain folds along the three wings at an angle of 30 degrees (left-handed people should make valley folds). Place the front side on top and warp all three wings a little upward. Do it so that when placed on an even surface, the tips of the wings protrude upwards a little (Figure 12). Place it so that you face the front side, and hold it so that you pick up the tips of the wing with your thumb and index finger (left-handed people should dothis facing theback side). Place the wings vertically as though flyingapaper plane or throwing darts, and throw it in a straight line along the eye. Make sure that you do not throw it pointing upward toward the ceiling. Give a snap to your wrists to give a spin to the boomerang. The swifter the spin, the better the boomerang will come back to the thrower (Figure 13). The boomerang turns leftward along the eye level (counter clockwise when seen from above) and returns (clockwise trajectory in the case of left-handed throwers). The distance flown is 3 to 4 meters, and the time in flights is 1 to
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WHY DO BOOMERANGS COME BACK? Yutaka Nishiyama ...

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