Force done by the spring if a weight is attached

AI Thread Summary
The discussion centers on calculating the force exerted by a spring when a mass is attached. The key equations used include F=ma, F=-kx, and Fg=mg. It is established that when the mass is at rest, the gravitational force (mg) and the spring force (Fs) must balance each other, leading to the equation Fs = -mg. The participants clarify that the spring force should be negative to indicate it acts in the opposite direction to gravity. Ultimately, the correct force done by the spring is confirmed to be Fs = -mg, emphasizing the importance of sign in force direction.
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Homework Statement



What is the force done by the spring if an object of mass m is attached.

Homework Equations


F=ma
F=-kx
Fg=mg


The Attempt at a Solution



Sum F = 0
mg-kx=0
mg-Fs=0
Fs=mg

Therefore the force done by the spring is mg? is the +/- right? for direction? Is the force right?
 
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Properly think about it:

The mass is hanging from the spring. I assume that when it is observed, it can be considered at rest.
If it's at rest, there are only two forces acting on the mass: gravity and the spring force. Since the mass is at rest, all forces must cancel each other.
.
Since both forces are acting in opposite directions, they shouldn't have the same sign.

You stated that Sum F = 0. Therefore, Fs + Fg = 0
 
Ok so then Fs=-Fg=-mg.
Just change the sign of my answer?
 
Yep.
 
ok thank you very much! i thought the sign was a bit messed up.
 

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