Test your skills of deduction with the September 2025 edition of Riddle Me This: Fans and Ping Pong
A large fan is mounted to the ceiling of a factory. It’s turned off and perfectly still. An engineer climbs up and places a ping pong ball on top of one of the blades. Then she turns on the fan remotely. The ball does not fall. Why not?
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I may be wrong, but I believe this only works if the fan is infinitely large (or friction so strong) that the ball doesn’t just slide off the end of the blade due to the centrifugal effect. I am not sure describing the fan as large is sufficient.
Did Chat GPT answer this? A ping pong ball on a ceiling fan blade has very little friction so as soon as you place it on the blade it will roll off due to the slant in the blade even before you have a chance to turn on the fan. Assuming you are able to turn the fan on immediately after placing the ball and maybe if you have the speed exactly right to generate the right amount of wind resistance and you operated the fan to blow upwards you could counteract the tendency for the ball to roll off. That would only last a few moments however until the ball worked its way off the end of the blade due to the ball moving tangentially to the circular moving blade. There would be negligible centripetal force acting on the ball itself.