NEET BIOLOGY

Detailed explanation-1: -Answer and Explanation: The forces that act on a dropped book are gravity and air resistance, also known as drag.

Detailed explanation-2: -Furthermore, as an object falls, it is being pulled downward by the force of gravity. At the start of the fall, the force of gravity is an unbalanced force. This causes the object to gain speed or to accelerate. As it accelerates, it encounters air resistance or aerodynamic drag.

Detailed explanation-3: -Gravity causes objects to accelerate downward, whereas air resistance acts in the opposite direction and reduces acceleration. Falling objects with a greater surface area experience more air resistance. In a vacuum, where there is no air, all objects fall with exactly the same rate of acceleration.

Detailed explanation-4: -Falling objects have two main forces acting on them, the force of gravity pulling them towards Earth and air resistance acting in the other direction and slowing their fall. The size of these forces change as an object falls, until the object reaches a constant speed, called terminal velocity.

Detailed explanation-5: -As learned in an earlier unit, free fall is a special type of motion in which the only force acting upon an object is gravity.