This is from educake but

For a certain spring, k = 15N/m. A weight is hung from the spring, stretching it from 0.3m to 0.4m. What force did the weight produce? what is the name of the force?

k = spring constant of the spring = 15 N/m

x₀ = initial position of the spring = 0.3 m

x = final position of the spring = 0.4 m

Δx = stretch in the spring

stretch in the spring is given as

Δx = x - x₀

Δx = 0.4 - 0.3

Δx = 0.1 m

the spring force balances the weight

hence

F = force by the weight

using equilibrium of force in vertical direction

force by weight = spring force

F = k Δx

inserting the values

F = 15 x 0.1

F = 1.5 N

the force by weight is also known as force of gravity.