A spring has stiffness of 100Nmm, the initial compression of the spring is 15mm, and it is then compressed to 65mm.
a)Find potential energy at 15mm:
K=100Nmm*1000=100000Nm
Ep=Kc^2/2
Ep=(100000*0.015^2)/2
Ep=11.25 joule (ans.)
b)Find Ep at 65mm:
Ep2=(100000*0.065^2)/2
Ep2=211.25 joule(ans.)
c)Find the work done during compression:
W.D.=Ep2-Ep1
W.D.=211.25J-11.25J
W.D.=200Joule
Hope this is correct, thank you for checking my work