An ideal spring of negligible mass is 12.00cm long when nothing is attached to it .when you hang a 3.15kg weight from it , you measure its length to be 13.40cm . If you want to store 10.0J of potential energy in this spring , what would be it's total length? Assume that it continues to obey Hooke's law .

Answer 1

the weight (force) of a 3.15 kg mass is ... 3.15 * g

find the spring constant (k) by dividing the force by the extension
... (3.15 * g) / (13.40 cm - 12.00 cm)

stored energy is ... 1/2 * k * x^2
... find x ... add it to 12

for Joules , the extension is in meters and the force is in Newtons