Concept of Lift and Drag!

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Concept of Lift and Drag!


George Cayley's theory.

The most crucial force responsible for the aircraft to fly is the lift force, so it’s necessary to know the concept of how lift is generated important.

To understand lift, imagine a cardboard. And let’s consider two situations:

  • You are holding cardboard perfectly horizontal against the wind.
  • You are holding cardboard tilted up making some angle with the horizontal against the wind.

CASE 1: You are holding cardboard perfectly horizontal.


            In this case you can see that the cardboard exerts a force on your hand (negligible) but do not exert any force in vertical direction and stays as it is. This force that pushes the cardboard back is due to cardboard opposing the flow of air. This force is known as ‘Drag’

CASE2: You are holding cardboard tilted up making some angle with the horizontal against the wind.



            In this case as soon as you hold the cardboard at some angle against the wind you see that the board is lifted in air and spins backwards. But why does it happen so?

When the cardboard is kept at an angle the wind hits the cardboard at an angle, this angle splits the resultant force generated in vertical axis and horizontal axis.

The component of resultant force generated in the vertical direction is called ‘Lift’. And as we can see from our experiment this is the force that helps to lift the cardboard up. This generated lift if is equal to the weight of cardboard, the cardboard can stay in air. This is the concept behind the airplanes staying in air.

The component of resultant force generated in the horizontal direction is called ‘Drag’. The drag force pushes the cardboard back. The drag is caused due to the cardboard opposing the flow of air.  To keep the cardboard in air at the fixed position the drag force which pushes the board back must be countered with a force that can pull the board font with the same amount of force as drag.

So, do aircrafts also generate lift in similar fashion using a cardboard mounted at an angle to horizontal?

Surprisingly yes, the cardboard is called wing and uses the same principle. But the cardboard is not just rectangular slab. It’s more than that. The cross section of wing is called airfoil. This airfoil uses the principle discussed here and also principles developed later i.e. Bernoulli’s principle to generate lift. But that’s a story for another blog! ;)

The concept discussed here was first proposed by George Cayley, who is sometimes known as the ‘Father of Aeronautics’.

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"With Great LIFT comes Great DRAG"