Chapter 13, Problem 40A

If you were unfortunate enough to be in a freely falling elevator; you might notice the bag of groceries you were carrying hovering in front of you, apparently weightless. Cite the frames of reference in which the groceries would be falling, and those in which they would not be falling.

To determine

The frame of reference in which the groceries would be falling and not falling.

Answer to Problem 40A

Groceries will be falling with Earth and not falling with the falling elevator.

Explanation of Solution

Introduction:

Weightlessness is the condition of the absence of support force or when the net forces exerted on the object is zero.

When a person is in a free-falling elevator, then groceries with the person hover in front of him. This is because of weightlessness acting on the groceries. Groceries will experience force with Earth i.e. combined system of groceries and the elevator will fall downwards.

But, it will not fall with the elevator that is net supporting forces experienced on the groceries will be zero. As the elevator free falling downwards, it will experience downwards force. But, the mass above the elevator will balance each other. Thus, groceries will not fall with the elevator.

Conclusion:

Thus, groceries will be falling with Earth and not falling with the falling elevator.