A spring with k=45 N/m is .35m when pulled(adsbygoogle = window.adsbygoogle || []).push({});

down with a 1.0 kg mass, what is the length of the

spring when the mass is taken off? The answer in the

back of the book is .13m (13 cm), I can't for the life

of me figure out how they get that.

I know that Hooke's Law is: F = -kx

What I've done so far:

F = (45)(.35) = 15.75 ---> Force it takes to pull down .35 meters, apparently using 1.0kg. Thus, if I divide 15.75 by 9.81, I should get 1.0kg, yes?

15.75 / 9.81 = 1.60 --->

I must be doing something wrong, lets start backwards.

F = (45)(.13) = 5.85 --> Force it takes to pull down .13 meters (this x is the answer, but right now i'm trying to find a proper F). 5.85 / 9.81 = .56, again, not 1.0kg. :(

What am I doing wrong? Can anybody point me in the right direction?

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Hooke's Law

**Physics Forums | Science Articles, Homework Help, Discussion**