If a spring stretches 0.9 m when a 3-kg weight is attached to it, how much will it stretch when a 4-kg weight is attached to it?

Answer 1

Assuming the spring obey's Hooke's law, then
force = k* (stretch distance)
from
3kg wt.=k*0.9m
we determine k=3kg.wt/0.9m=(10/3) kg.wt/m
So for 4 kg wt, we have
4 kg.wt=(10/3)*distance
Solve for distance.