# Could you walk across a swimming pool filled w/ ping pong balls?

In summary, Matt's brother insists that the balls would support a person who could easily walk across, but Matt says that this would not work because the balls, being so light and having a smooth sphere shape, would cause a standard person to sink into the balls and one would have to "wade through" them to get out of the pool.
Hello,

I feel a little out of place here, as I have no physics background whatsoever, but I was hoping you folks here might be able to help settle a debate. My brother and I like to have "what if" discussions, and one we had quite awhile ago was whether a person could walk across a swimming pool filled with ping pong balls (EDIT: No water in the pool, only ping pong balls).

I said that it would not work, because the balls, being so light and having a smooth sphere shape, would cause a standard person to sink into the balls, and one would have to "wade through" them to get out of the pool.

My brother, however, insists that since the balls would be supported by the sides and bottom of the pool, they would support a person who could easily walk across.

If this is too unscientific of a question feel free to ignore or delete it, but this debate has been going on for quite awhile and I was hoping that someone more experienced in weight/friction/physics issues could explain what would happen better than myself. Thanks for your time,
Matt.

Last edited:
You are correct, and your brother not so much. Challenge him to walk over ping-pong balls on dry land and see how far he gets. Water just bitches it up a couple of notches.

Danger said:
You are correct, and your brother not so much. Challenge him to walk over ping-pong balls on dry land and see how far he gets. Water just bitches it up a couple of notches.

I should have clarified: The pool is full of ping pong balls only, no water involved. But I don't believe either way would work...

Thanks for the response.

Yes, you would sink. When you walk, your weight is spread over the area of your feet. Assuming that your foot covers 10 balls and you weigh 150 pounds, each ball is roughly exerting 15 pounds of force in some direction when you take your first step. Since the other balls can't go down, this would result in them rising up around your foot and you would sink.

In order to walk on ping pong balls, you would have to spread your weight over a larger area by using snowshoes or something like that.

We could always try looking at Archimedes Principle!
The standard mass of a ping pong ball is 2.7g and its diameter is 40mm
This gives it an effective density of about 0.08 g/cm3
The density of water is 1 g/cm3

Conclude from that what you will.

Ball pools wouldn't be much fun if you could walk on the surface!

Stonebridge said:
We could always try looking at Archimedes Principle!
The standard mass of a ping pong ball is 2.7g and its diameter is 40mm
This gives it an effective density of about 0.08 g/cm3
The density of water is 1 g/cm3

Conclude from that what you will.

I would think the question is about viscosity, not buoyancy.

Well, Matt edited his OP to mention that there was no water involved, but I still think that it can't be done. It would be extremely easy to "float" upon the balls in a horizontal position, but I can't see any way in which one could remain vertical.

russ_watters said:
Yeah, jeez - have you guys never been to McDonalds?!

Uhhh, no... and why have you?

Hurkyl said:
I would think the question is about viscosity, not buoyancy.

Me too. I was being mischievous.
Can you think of a simple order of magnitude calculation involving viscosity of ping pong balls?

Borg said:
Yes, you would sink. When you walk, your weight is spread over the area of your feet. Assuming that your foot covers 10 balls and you weigh 150 pounds, each ball is roughly exerting 15 pounds of force in some direction when you take your first step. Since the other balls can't go down, this would result in them rising up around your foot and you would sink.

In order to walk on ping pong balls, you would have to spread your weight over a larger area by using snowshoes or something like that.

Exactly! At one point I mentioned to him that unless one was wearing something that made their feet very wide, it would be impossible.

I appreciate the responses everyone. Thanks for your help.

Any time, pal. Hang around for a while and get into some other neat ****. You strike be as being someone who will be a great PF member.

## 1. Can a person actually walk across a swimming pool filled with ping pong balls?

Yes, it is possible for a person to walk across a swimming pool filled with ping pong balls. However, it would be extremely difficult and would require a lot of balance and coordination.

## 2. How many ping pong balls would it take to fill a standard swimming pool?

The number of ping pong balls needed to fill a standard swimming pool would vary depending on the size of the pool. However, on average, it would take around 25,000 to 50,000 ping pong balls to fill a standard sized pool.

## 3. Would the ping pong balls be able to support a person's weight?

No, ping pong balls are not strong enough to support a person's weight. If someone were to try and walk across the pool, they would likely sink or fall through the balls.

## 4. How would walking across a pool of ping pong balls affect the balls?

Walking across a pool of ping pong balls would likely cause the balls to shift and move around, creating gaps and spaces for the person to fall through. The balls may also become crushed or damaged under the weight of a person.

## 5. Are there any safety concerns with walking across a pool of ping pong balls?

Yes, there are several safety concerns with walking across a pool of ping pong balls. The balls could pose a slipping hazard, and if someone were to fall through the balls, they could potentially get injured. It is not recommended to attempt walking across a pool of ping pong balls without proper safety precautions in place.

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