# how gliders fly

GliderForces

How gliders fly

What makes it fly? What forces act upon an airplane in flight? Study the forces acting on an object in flight by experimenting with paperclips to find out how they affect flight.

Four forces (gravity, lift, thrust, drag) are the forces acting upon a plane in flight. The most difficult force to explain will be the concept of lift and the Bernoulli Principle that governs it.

In an ACTUAL plane more that 3/4 of the entire weight is held up by the air flow on the top of the wings. This is because of Bernoulli’s Principle which states that when air moves faster across the top of a wing the pressure of the air pushing down is less than the pressure pushing up, thus creating lift.

• Using the smaller card, hold it high over your head and release it with a gentle push. As the card falls, its flight pattern will be erratic and random. Repeat this flight several times.
• place a paper clip at the center of one of the longer edges of the card. Place the small end of the clip at least a quarter of an inch from the edge.
• Repeat the flight test adding one paper clip until the glide path of the card becomes constant.

How many paper clips did it take for your card to become stable?

If your platform were an aircraft, would a heavy weight load be desirable if you had another method of insuring stability? Of course not. Since your platform is now stable, but heavy with paper clips, you are now ready to experiment with the use of dihedral angle. Use of the dihedral may allow you to remove some of the paper clips.

• Fold your card in half using the axis which goes through your paper clips. The platform should have a V shape.
• Using the card create a dihedral and use enough paper clips to make it stable. How many clips did it take for the platform to become stable?

Materials Needed: Two index cards (one 3×5 and one 5×8); eight or nine paper clips