Planes are really cool, and flightmonkeys.com is one of the best kid-friendly sites to go to. Today, I will talk about the four forces of flight.
The four forces of flight include:
Notice how these four are paired. The lift has to counter the weight. If the lift is the same or lower than the weight, it won't fly. When you drive to/from work today, stick your hand out the window. Do you feel the drag? Planes go through this everyday. They have to have more thrust than the current drag. The faster it goes, the higher the drag. Soon, the drag will be the same as the thrust, so it will stop accelerating. Here's a picture: