✔ 最佳答案
use hooke's law, find the elastic modules of spring
F=kx
k=(18-3)/(10.8-8.8)
k=7.5
when F=3
x=3/7.5=0.4 (the spring is moved 0.4cm from inital position point)
inital length of spring=8.8-0.4=8.4cm
when F=10,
x=10/7.5=1.33
length of spring=8.4+1.33=9.73cm