What is spring constant ? What are its SI units?

Explanation

### Step-by-Step Solution:

1. **Definition of Spring Constant**:
The spring constant, denoted as \( k \), is a measure of the stiffness of a spring. It quantifies the relationship between the force applied to a spring and the displacement (elongation or compression) of that spring from its equilibrium position.

2. **Mathematical Representation**:
The spring constant can be expressed using Hooke's Law, which states:
\[
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