Conceptual Spring Problem

1. Jan 5, 2010

collegeconfid

1. The problem statement, all variables and given/known data
A spring (in equilibrium) is attached to the top of a box that is moving at a constant speed vertically upward.
However, if the box stops, does the spring go upward or downward?

2. Relevant equations

3. The attempt at a solution

The spring goes downward because originally, the force being exerted on the spring is the spring force and gravity. But, when the box is stopping, there must be an extra downward force to slow the box down, so once the box stops, there will be a net downward force.

Logically, I would imagine the spring going upward but...

The answer is that the spring will go downwards. Is this the correct reasoning?

All replies are much appreciated.

EDIT: Sorry if I wasn't clear enough before, but the spring is inside the box and is hanging from the top of the box.

Last edited: Jan 5, 2010
2. Jan 6, 2010

ideasrule

That's true, but a net downward force means a downward acceleration. It doesn't mean a downward speed.

That's correct. The spring initially keeps whatever speed it had before the box stopped, so it's still going upward when the box stops.