Science Buddies: "Ask an Expert"

I am a 7th grader intrested in the areodynamics of hovercrafts.
How is a hovercraft aerodynamic?
Does the mass of a hovercraft affect the performance?
How could the design of a hovercraft affect performance?
How does the air cushion feduce friction of the hovercraft in motion?
Thank you for taking time to answer my questions.

Have you done any online research and reading on hovercraft yet? If not, then start there as most of your questions can be answered by some easy reading.

How is a hovercraft aerodynamic?

If you define aerodynamic as something that moves easily through the air with little drag, then hovercraft are NOT aerodynamic. Unfortunately, I've introduced a new term, aerodynamic drag. Look it up.

Does the mass of a hovercraft affect the performance?

The mass of anything affects its ability to change directions and speed and the force required to do so. Mass also affects the gravitational force which is the force it takes to lift the object. Read up on Newton's laws of motion.

How does the air cushion reduce friction of the hovercraft in motion?

Is this a trick question? What is the definition of friction? The ususal definitions for friction involve the force required to slide or rotate some object across the surface of another object. If the hover craft is hovering on air, the only thing the hover craft is sliding or moving over is moving air. But the air is moving over both the hover craft skirt and the ground. You can define friction like forces for fluid flows but that gets into some very complicated areas of physics called fluid dynamics and thermodynamics. But the hovercraft skirt can come in contact with the ground in motion and then there would be clasic friction but only for that portion of the skirt that came in contact with the ground and only for that time that it is in contact with the ground and in motion with respect to the ground. Tricky situational definition!

Hi,

Please refer to Craig's post as most of your questions are answered there.

Regarding "How could the design of a hovercraft affect performance?" --

Essentially the capability of the hovercraft to function and to be efficient will depend on its center of mass, how spread out it is, etc. Certain designs will require more air to stay afloat and some will require less, which factors into the performance.

Hope this helps,

Manjinder