Can some explain thrust, drag, lift and weight?

Question

can someone elaborate give a few sentences on these words relating to aerodynamics.

Drag:

Thrust:

Lift:

Weight/Gravity:

I'm hoping to use this information to build paper planes

thanks guys

Answer 1

In basic terms of you making paper aeroplanes:

Thrust = How hard you throw it into the air, maximised by releasing the aeroplane at the highest speed you can.

Drag = Newton's 3rd law, the aeroplane hits the air so the air hits it back, this slows it down. Drag is minimised by minimising surface area however surface area is required to provide lift.

Lift = Force pushing the aircraft upward. In a real aircraft flaps are used during takeoff to make the air flowing over and under the wing move downward at the trailing edge (rear of wing). Newton's 3rd law again.... air pushes downward so the wing moves upward. Lift is maximised by enlarging wing surface area, the more air flowing over it the bigger the lift force, nothing's perfect of course, more wing means more weight!

Weight: The more massive the aeroplane i.e. the more paper then the more stuff there is for gravity to pull on. Weight =  mass x 9.81 on earth. Weight is therefore minimised by reducing mass.

So to make the best paper aeroplane you have to find the best comprimise between all of these factors. You can add surface area which will increase flight time more that it will be reduced by air resistance if you add surface area aerodinamically. Just use the lightest, strongest paper you can find!

Answer 2

Drag:  This is the force that opposes forward motion. It is a combination of parasite and induced drag added together.  Parasite drag is the result of skin friction as air moves across the body of the plane.  Induced drag is the result of lift.  Some lift always acts backward and that tends to slow the plane down.

Thrust:  Thrust opposes drag and helps to move the airplane forward.  It is produced by the propeller.  As air is grabbed by the propeller and thrown backward by it, an equal and opposite reaction occurs whereby the plane os moved forward.

Lift:  Lift is the result of airflow over the wings.  It is a far too complex subject to "define" lift in a few sentences, but it is produced by the wings and acts approximately upward in opposition to gravity.

Weight:  Weight is pretty self explanatory.  However absolute weight is not the same as measured weight.  When aircraft enter into turns or banks, they gain additional weight called load factor.  The load factor it 1 in a straight and level turn and 2 in a 60 degree banked turn (and about 9 in an 80 degree bank).  Also, the horizontal stabilizer acts as an inverted wing stabilizing the flight path of the plane by pushing the tail down.  This additional weight must also be overcome aerodynamically.

These four forces are said to be in balance when an aircraft is in straight and level, unaccelerated flight.  When the aircraft is not speeding up, slowing down, climbing, descending, or turning, thrust equals drag and lift equals weight.