When you drop a ball, it bounces back up, but not to the same full height. What happens if you drop a ball on top of a ball on top of a ball? Physics Girl stacked up a golf ball on top of a bouncy ball on top of a basketball. When she dropped the stack, the basketball and bouncy ball rocketed the golf ball way up into the sky – 28 feet! That’s more than 8 times the height the golf ball started from – or a tower of 35 basketballs, or 200 golf balls.
Wee ones: Find a ball of any size. Drop it without throwing it down, and see how high it bounces. Does it bounce as high as your hand?
Little kids: If 3 friends each drop a stack of 3 balls, how many bouncing balls is that? Bonus: If each story of a building is 10 feet tall and you stand on the roof of a 2-story house, does that golf ball bouncing to 28 feet stop above or below you?
Big kids: If this stack made the golf ball fly 8 times its starting height, how high would the golf ball fly if a stack was dropped from a 20-foot-tall diving board? (Onto the pavement, not into the pool!) Bonus: What if you could bounce 8 times your height? How high would that be in feet and inches?
Wee ones: You can try any ball – a rubber ball, soccer ball, tennis ball – but no matter how bouncy it is, it will not bounce to the full starting height.
Little kids: 9 balls. Bonus: It will bounce higher than you, since you will be just 20 feet above the ground.
Big kids: 160 feet. Bonus: Different for everyone…You can either multiply the feet and inches each by 8 separately and then figure out the extra feet, or you can take the total in inches and multiply that by 8. A neat shortcut: you double the number, then double again, then double it one more time, because 2 x 2 x 2 = 8.
Laura Bilodeau Overdeck is founder and president of Bedtime Math Foundation. Her goal is to make math as playful for kids as it was for her when she was a child. Her mom had Laura baking before she could walk, and her dad had her using power tools at a very unsafe age, measuring lengths, widths and angles in the process. Armed with this early love of numbers, Laura went on to get a BA in astrophysics from Princeton University, and an MBA from the Wharton School of Business; she continues to star-gaze today. Laura’s other interests include her three lively children, chocolate, extreme vehicles, and Lego Mindstorms.