Science Buddies: "Ask an Expert"

Hello,
For my science project, I am trying to discover the effect of fuzz on a tennis ball. I used a wind tunnel, and I have all of my data. I measured the amount of drag an old tennis ball created, a shaved tennis ball's drag, a normal tennis ball's drag and a tennis ball with extended fuzz's drag. I just need a few questions answered, before I continue.

1. How would the fuzz of a tennis ball effect the airflow around the ball? Why?

2. Would the fuzz on a tennis ball effect the lift as well, or would it not? Why?

3. How might the spin of the tennis ball effect the drag of the ball? And the lift?

4. Are there any other laws/principles apart from Bernoulli's Principle? If so, what is the name/s and what are it's rules?

5. Is the drag of the tennis ball amplified by the speed it is traveling, or no? Why?

Thank you for answering.

Hello, [email protected]
I used to be a Science Teacher, and although I don't know aerodynamics to an "Expert" point, I can certainly help you. (I also play a bit of tennis)

1. The fuzz would interupt the tennis ball's airflow, making the airflow less smooth and more... chunky. This would cause more drag, and most probably less lift.

2. The fuzz on a tennis ball would most probably effect the lift as well. Remember, the more drag, the less lift. When the ball would be traveling in the air, it would get more drag and less lift if there was more fuzz.

3. Spin has a lot to do about the lift of a tennis ball, as well as the drag. If the ball is spinning forward, it is pushing more air towards the front of it, making it have less lift and more drag, meaning that it would land sooner than a ball without spin. If the ball was spinning backwards, the air would be pushed behind it, creating more lift.

4. None that I know of, sorry. You should look that up, as I am sure there are more.

5. Yes. If a ball is traveling faster, the drag grows, creating more friction on the ball. The ball will slow down faster than a slower traveling ball. (This is the dangerous part of lobs in tennis, as they normally travel slow, and slow down a lot slower.

I hope I answered your questions well. Good luck on the project!! It sounds interesting.
-Bill Harley