# B Quiz Question -- What happens to the cork?

1. Aug 10, 2017

### zul8tr

You have a glass of water with a cork floating in it. The cork is attached by a spring under some tension that is also attached to the bottom of the glass so the cork is slightly pulled deeper in the water than just by its own weight thus the cork has a bit more buoyant force. The cork always remains centered in the glass.
If the glass is dropped free fall and remains vertical and no water spills out what motion does the cork do relative to the glass wall, obviously before it hits the ground? Go up, down, remain the same and why?

2. Aug 10, 2017

### Staff: Mentor

What do YOU think happens and why?

3. Aug 10, 2017

### zul8tr

I know the answer wouldn't want to give it away too soon, needs others to solve.

4. Aug 10, 2017

### Staff: Mentor

Thread closed for Moderation. We often do not allow quiz questions like this because they could be disguised homework assignments. Given you user Profile, I doubt it is homework. Please start a private conversation with me (click my avatar and "Start a Conversation") and let me know your solution. If it looks good, I can re-open the thread.

5. Aug 11, 2017

### Staff: Mentor

Thank you for the PM and for your patience. Thread is re-opened as a Quiz Question.

6. Aug 11, 2017

In the free fall there is no buoyant force, so the spring should go back to the zero position, and the cork will of course go downward as the spring pulls it down. Good question @zul8tr . I answered quickly without giving it very careful analysis, but I think I may have gotten the correct answer. :)

7. Aug 11, 2017

### CWatters

Down.

8. Aug 11, 2017

### Staff: Mentor

Down to the relaxed position of the spring, a conclusion that will be altogether natural if you consider that the water will tend to drift out the glass leaving the spring behind.

9. Aug 11, 2017

### zul8tr

Down is the correct reaction of the cork. Internal spring force is all that is acting on the cork, free fall has reduced buoyancy to zero