The correct answer is option 4: The brick will fall with constant speed for some time and then with constant acceleration as it nears the earth.

When the brick is thrown vertically from the aircraft, it initially has an upward velocity due to the force applied to it. However, once it leaves the aircraft, it will begin to experience the force of gravity pulling it downward.

Initially, the brick will fall with a constant speed as it accelerates due to gravity. This is because the force of gravity is balanced by the air resistance acting on the brick. As the brick gains speed, the force of gravity will eventually become greater than the air resistance, resulting in an unbalanced force and causing the brick to accelerate further.

As the brick nears the earth`s surface, the force of gravity becomes the dominant force, and the brick will continue to accelerate with a constant acceleration due to gravity. This is because the force of gravity remains constant and the mass of the brick does not change significantly.

It is important to note that acceleration is the rate at which velocity changes, and in this case, the velocity is changing due to the force of gravity. Therefore, the correct option is option 4: The brick will fall with constant speed for some time and then with constant acceleration as it