# Force needed to extend or compress a spring

## Force needed to extend or compress a spring having radius say r and cross-sectional area A by distance say X is proportional to _____.

a. diameter of the spring wire

b. cross-sectional area of the spring

c. change in distance X

d. none of the above

Correct Answer : c. change in distance X

**Explanation :**

According to Hook's law F = -kX , where k is constant. Therefore force needed to extend or compress a spring is directly proportional to the distance X.