- #1
masterchiefo
- 212
- 2
Homework Statement
The spring of a dynamo-meter grows 20cm when one suspends a 4N on weight. What is the potential energy of the spring when one suspends a weight of 12N?
Homework Equations
Ue = 1/2*k*r2
Ug= m*g*h
The Attempt at a Solution
so to find k I do this step.
1/2*k*0.22 = 4*0.2
k=40N/M
Now that I have k I can find the potential energy of the spring with 12N
1/2*40*r2 =12*r
I find r to be 0.6
now I do 12*0.6 = 7.2J to fnd the potential energy of the spring.
The real answer is 3.6J but I can't figure out how to get this.