It took 1800 J of work to stretch a spring from its natural length of 2m to a length of 5m. Find the spring's force constant.

Please help. Thanks in advance.

2 answers

Start with the definition of spring constant
F(x)=kx
From the definition of work,
W=∫F(x)dx
W=∫F(x)dx=kx²/2 + C
The spring has stretched from its natural length (x=0) to 3 m longer:
1800=(k/2)[3²-0²]
Finally, solve for k
k=2*1800/9=400 j/m
why F(x) = K x ?