Five boxes,each having weight 100 N,are stacked up.The bottom box is the fifth from the top.What is the magnitude of the normal force upward exerted by the fourth box from the top on the third box from the top?
A)100 N
B)200 N
C)300 N
D)400 N

Question

Quizplus · Accepted Answer

Since each box has a weight of 100 N, the total weight of the five boxes is 500 N. When they are stacked up, the bottom box experiences a normal force of 500 N from the ground. This normal force is transmitted through the boxes above it, resulting in a decreasing normal force as we move up the stack.

Therefore, the fourth box from the top is experiencing a normal force of 200 N (from the box directly below it) and is exerting a downward force of 200 N on the third box from the top. However, the third box from the top is also experiencing a normal force of 100 N from the box directly below it.

Thus, the net normal force exerted by the fourth box from the top on the third box from the top is 200 N - 100 N = 100 N.

Therefore, the correct answer is:

C) 300 N

Five Boxes,each Having Weight 100 N,are Stacked Up