about AL phy (matter )measur yong modulus of copper(20marks

Okay, as an engineer, i will tell you this,
Young modulus, will tell us more on the material property, an as we told the young modulus, we can predict the material graph immediately, and young modulus can help us on safety factors!
Force constant are more useful on the plastic material side, as a steel engineer, we concern more on the young modulus, for our material selections!

Young's modulus, E
= F L0 / A0 L0
E is the Young's modulus (modulus of elasticity) measured in pascals;
F is the force applied to the object;
A0 is the original cross-sectional area through which the force is applied;
ΔL is the amount by which the length of the object changes;
L0 is the original length of the object.

F=(EA0/L0) ΔL
F=k x
i.e. EA0/L0 = k , the force constant

it means it considered more parameters - dimensions
cross-sectional area and length...