Why does an airplane run a certain length on the runway first before taking off?

(N/A) An airplane wing is designed with a special shape called an airfoil. As the airplane moves along the runway,air flows over the top and bottom surfaces of the wings. Due to the shape of the wing,the air velocity at the top is higher than at the bottom. According to $Bernoulli's$ principle,where the velocity of a fluid is higher,its pressure is lower. Thus,the pressure at the top of the wing becomes lower than the pressure at the bottom. This pressure difference creates an upward force known as lift. Once the airplane reaches a sufficient speed,the lift force becomes greater than the weight of the airplane,allowing it to take off.