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The Ultimate Bottle Toss Challenge

Did you know that there is a science behind finding the ideal water bottle type and water level to flip and land a water bottle on its base? Our 4th and 5th grade students for the last five weeks during STREAM Friday activity time have taken the challenge to discover the best water bottle flip scientifically.  Students tested 4 different water bottle brands with varying bottle heights, shapes, and levels of water (either half or a third full) in the bottle.  Students then practiced tossing the bottles with a specific flip technique for the same predetermined amount of times.  Using mathematics, students used fractions and percentages to determine the highest successful toss rate, and graphed their results.  Students then used iPads to record themselves flipping the bottles, and viewed the bottle flip in slow motion to see how gravity, the center of mass, and angular momentum effect the rotation and successful landing of the bottle.

Here’s the scientific explanation: 1) When holding a water bottle from the top, the water is at the bottom of the bottle and so is the center of gravity. 2) When you toss the bottle, it rotates, but the water does not rotate with it.  This is because water flows freely and has space to slosh around. 3) As it spins, the bottle pushes against the water and the angular momentum is transferred to the water. But the water is much heavier than the bottle and the rate of rotation starts to slow down. 4) The bottle will fall with gravity and land straight up on the table if it stops spinning at about the same time as the water collects in the bottle.

Our students’ results: They found that the “Sam’s Choice” (20 oz) bottle filled with 10 oz of water worked the best to flip and consistently land on its base.