Paper Tent

SCIENCE CONCEPT:

A way of understanding the deflection of air by an airfoil is by applying Newton's third Law of Motion. The airfoil deflects the air going over the upper surface downward as it leaves the trailing edge of the wing. When the wing is at an angle, this deflection is even greater. According to Newton's Law, for every action there is an equal, but opposite reaction. Therefore, if the airfoil deflects the air down, the resulting opposite reaction is an upward push.

STUDENT OBJECTIVE:

The student will explore how an airplane stays up in the air by making a paper tent and doing experiments with it.

OVERVIEW:

In this activity, the student will use a paper tent about 5 inches by 8 inches and blow on it in different ways to create the same air flow that happens on the airfoil of an airplane to prove how an airplane stays up in the air.

PREPARATION TIME:

5 minutes.

LESSON TIME:

15 - 20 minutes.

TEACHER PREP:

Cut stiff paper 5 inches by 8 inches, one for each student.

WORDS TO KNOW:

deflection

airfoil

trailing edge

action and reaction

cambered wing

lift

leading edge

angle of attack

TEACHER TEXT:

Deflection is an important source of lift. There are some planes that do not have cambered wings ( cambered wing is curved). Their wings are flat and are designed to fly at very high speeds. These planes get lift only by deflection. Planes flying upside down, even with cambered wings, can deflect enough air to get lift.

The amount of lift a wing can produce is governed by several factors. First, the weight of the object to be flown. Second, the size of the under surface of the wing. The larger the wing the more lift produced. Another way to increase the lift is to change the angle of the wing as it faces the air. This is controlled by the pilot of the plane and is called the plane's attitude. By tilting the leading edge up, the distance the upper air stream must flow is even greater: upper air speed increases, thus lowering pressure above the wing and creating more lift. This is called the angle of attack. Two times the angle of attack equals two times the lift. Increasing the lift means the plane can climb faster or fly at a slower speed.

Speed is the most important element in producing lift. Speed can be increased by increasing the forward speed of the wing itself as it travels through the air. This causes an even more dramatic change in lift. If you double the speed, you get 4 times the lift. Triple the speed and you get 9 times the lift.

The weight of the object desiring to fly, determines how much lift is necessary. Contributing to this, is whether the object is going up, down, or in level flight. When going up, lift must be greater than weight. In level flight, lift must equal weight, and going down lift is less than weight. Minimum speed for lift is dependent upon the design of the flying object.

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Last modified: Sat Dec 13 15:36:29 PST 1997