# Wind Tunnel

Air. It’s one of those substances that people can’t live without. However, the presence of air also acts as a hindrance when objects, such as cars, have to travel through it. Vehicle designers must create shapes that cut through air with the least amount of resistance. Can you find out which shape offers the smallest amount of air resistance? Take a big gulp of air and get started.

### What is air?

Air is a mixture of gases, primarily nitrogen and oxygen. About 78% of air consists of nitrogen gas, while almost 21% of air is composed of oxygen gas. Argon gas, carbon dioxide gas, water vapor, and some other gases make up the remaining percentage of air.

### What is friction?

Friction is a force that opposes the motion of an object. Friction is caused when two surfaces or substances moving in opposite directions collide. The collisions result in a force being applied to the moving object in the opposite direction of its travel.

### What is air resistance?

Air resistance is a type of fluid friction experienced by a solid object as it moves through air. In reality, it doesn't matter if the solid moves through air or the air moves past the solid. In both cases, the air particles collide with the solid object and apply a force in the opposite direction of the motion. This force slows down the motion of the particles or the object, whichever is moving. The more dense the fluid, the greater resistance offered by the fluid. So an object moving through air with a greater density would result in greater resistance, assuming that all other factors are held constant.

### What is drag?

Drag is the opposition to the motion of an object caused by resistance due to air. A moving car encounters drag, which acts to slow down the car. As the speed of an object increases, the amount of drag on the object also increases. The size and shape of an object can also affect the amount of drag experienced by the object as it moves through air. Since space is nearly void of air, no drag exists in space to slow vehicles down.

### What is turbulence?

Laminar or streamline flow is found when an object moves through air and the layers of air move at the same speed and same general direction. On the other hand, turbulent flow occurs when the air layers move in a disorganized fashion and create small eddies. This causes the air particles to move in various directions at different speeds and bump into each other. This increases the air resistance and generally slows a moving object down.