Human beings have long wanted to fly in the sky. After inventors’ constant study, trial and error, the plane was finally born, and today there are very large aircraft flying around the world, which can carry more than 700 passengers. A passenger plane such as A380 and B777 has more than four million parts and weighs hundreds of tons. Then, how can a plane fly in the sky with this tremendous weight?
There are four forces acting on the plane: the force moving forward (thrust), the force pulling to the ground (gravity), the force lifting upward (lift force), and the force acting in the opposite direction (drag). In order for the plane to take off, the lift force of the wings must be greater than the gravity. For this, the plane must run at high speed because thrust generates the lift force. If it is a large passenger aircraft, it will need about 3 ㎞ (1.86 mile) runway and the speed of 300 ㎞/h (186 mph) for takeoff. In short, it cannot fly without running.
People often compare the accomplishment of their dreams to flying in the sky. As an airplane takes off after running hard, so your dream will come true at a certain moment if you keep running toward the goal, like flying in the sky.