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A free-body diagram for a 20,000-kg airplane at some instant is shown in the animation (grid size is given in 40,000 newtons). Generally, all of the external forces on an airplane can be resolved into four components called weight, lift, thrust, and drag. Restart. You can move a vector around by click-dragging at its tail.

1. What is the net force on the airplane at this instant?
2. What is the acceleration of the airplane at this instant?
3. What can you definitely say about the velocity of the airplane at this instant?
4. Suppose a classmate in your study group proclaims that "the net force on the airplane is zero and therefore the airplane must be on the ground and at rest." What is the error in your classmate's statement?

Problem authored by Aaron Titus.