Solve Spring Constant: 40g Mass, 20N/m

[ajmCane22]

Homework Statement

A mass of 40.0 grams is attached to a vertical spring with a spring constant k = 20.0 N/m and lowered slowly until the spring stops stretching. How much is the spring stretched?

The Attempt at a Solution

I assume I have to use F = -kx? But I don't know the force so how would I figure this out? I am really stuck. Please help.

 

[Doc Al]

Hint: How much does the mass weigh?

 

[ajmCane22]

40.0 grams, but how is that a hint? F = ma and I don't know acceleration, so how does the mass help?

 

[Doc Al]

Given a mass 'm', how do you figure out its weight? What gravitational force acts on it?

 

[ajmCane22]

Would it be F = mg? It said the spring was lowered slowly so I assumed the acceleration was slower than gravity.

 

[Doc Al]

Would it be F = mg?

Yes!

It said the spring was lowered slowly so I assumed the acceleration was slower than gravity.

mg gives the weight of an object regardless of its acceleration. (If the object were dropped, so that the only force acting was gravity, then its acceleration would be g.)

 

[ajmCane22]

Thanks! :)