Final answer:
To determine the normal force on stacked objects, Newton's Second Law should be used, which states that the net force is equal to the mass times acceleration. When the objects are at rest, the normal force is equal to the combined weights of the objects.The correct option is A.
Step-by-step explanation:
To find the normal force on stacked objects, the physical principle that should be considered is Newton's Second Law. This law states that the net external force acting on an object is equal to the mass of the object multiplied by its acceleration (Fnet = m × a). In the context of normal force, when objects are stacked and at rest, the acceleration in the vertical direction is zero, which simplifies the application of Newton's Second Law.
For example, consider a book resting on a desk. The book exerts a downward force equal to its weight (W), and the desk exerts an upward normal force (N). If the book is at rest, these forces are equal in magnitude but opposite in direction, which is consistent with Newton's First Law (the state of rest). However, it is by applying Newton's Second Law (considering vertical acceleration is zero) that we can conclude the magnitude of the normal force is equal to the weight of the book. Applying this concept to stacked objects means summing the weights of all objects to determine the normal force exerted by the surface at the bottom of the stack.