Floating Bowling Balls Do bowling balls float? email to friend
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Today we will finally answer the question that has puzzled viewers for years: do bowling balls float? Not so fast - you'll have to see it to believe it! Plug the drain, fill the sink with water, and take the plunge with Steve's floating science challenge. We all know that certain things float in water while other things sink, but why? Do all heavy things sink? Why does a penny sink and an aircraft carrier floats? Think you know the answers? Well, get ready for a few amazing surprises!

If you've ever been bowling you know that bowling balls range from about 8 to 16 pounds. However they are all the same size! According to the official bowling rules, "The circumference of a ball shall not be more than 27.002 inches nor less than 26.704 inches, nor shall it weigh more than 16 Ibs (no minimum weight)." This means that the average density of an 8 pound ball must be HALF the average density of a 16 pound ball. In general, bowling ball manufacturers vary the size, shape and material of the core of the ball to adjust the weight. Enough about bowling balls! Let's try the experiment.

Materials

- A bowling ball weighing 9 pounds or less
- A bowling ball weighing 11 pounds or more
- A large aquarium or a bath tub filled with water

Experiment
Video

1. The next time you're at the bowling alley, sneak an aquarium filled with water in under your coat. Too risky? Ok, just collect a few bowling balls of various weights (from 8 to 16 pounds).

2. Fill the aquarium three quarters full with water.

3. Carefully place (do not drop!) the bowling ball in the water. Does it float or sink? Repeat this experiment, noting the weight of each bowling ball, until every ball has taken the plunge.

4. What did you discover? It seems that anything heavier that 12 pounds will sink, but bowling balls between 8 and 12 pounds float. Amazing!

How does it work?

Let's start with some properties of water. How heavy is 8 pounds? It just happens to work out that one gallon of water weighs 8 pounds. Hmmm? Something smells a little fishy because 8 pound bowling balls float. If one gallon of water weighs 8 pounds and an 8 pound bowling ball takes up more space than a gallon of water, the ball will float! What did Archimede say about all of this? When an object is placed in water it will displace it's weight in water. The 8 pound ball is displacing 8 pounds of water. However, the ball also takes up more volume than 8 pounds of water, so it floats. It might be less confusing to simply say the 8 pound ball is less dense than water and the 16 pound ball is more dense than water where density is the mass of the ball divided by its volume. Hey, are you pulling my leg? NO! The bowling balls that we used on television were legitimate, competition-sanctioned bowling balls. For those disbelievers, the water was real, too. We suggest using an 8 pound ball for your less dense ball since it floats fairly high but a 9 pound ball will work just as well. A 10 pound ball will almost "hover" in the water! Anything heavier than 11 pounds will sink. You might want to stop by your local bowling alley to see if the pro shop is throwing away any old bowling balls that you might be able to use for your science entertainment pleasure.

Additional Info

Teacher Comment - Read this!
I thought I should pass on the funny thing that happened at my son's bowling party last weekend... I asked our hostess if bowling balls float or sink :) She said "Well wouldn't they sink?" I then told her the mystery of the floating/sinking balls. She immediately goes to tell the long time owner and bowling aficionado . Together they go to the back room in disbelief and fill their sink with water, only to see the truth. I said I should get my bowling party for free now that I armed them with useful bowling trivia, AND she comped two of my bowlers!! YIPPEE!! Thanks for the useful tip.
-Diana Matthews