- #1
bob tran
- 17
- 0
Homework Statement
It requires 49 J of work to stretch an ideal very light spring from a length of 1.4 m to a length of 2.9 m. What is the value of the spring constant of this spring?
Homework Equations
u=0.5kΔx2
The Attempt at a Solution
[tex]
u=\frac{1}{2}k\Delta x^2\\
k=\frac{2u}{\Delta x^2}\\
k=\frac{2*49}{(2.9-1.4)^2}\\
k=44 \ \texttt{N}/\texttt{m}
[/tex]
Apparently, the answer is 15 N/m.
EDIT:
It appears they have done this instead:
[tex]
u=\frac{1}{2}kx_f^2 - \frac{1}{2}kx_0^2\\
u=\frac{1}{2}k(x_f^2-x_0^2)\\
k=\frac{2u}{(x_f^2-x_0^2)}\\
k=\frac{2*49}{(2.9^2-1.4^2)}\\
k=15 \ \texttt{N}/\texttt{m}
[/tex]
I thought Δx would be squared after the subtraction?
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