Hooke's law

Need to know

What you need to know

• $T$: Tension (or Thrust) in the string/spring, measured in Newtons (N). This is the restoring force exerted by the material.
• $\lambda$: Modulus of Elasticity, a constant specific to the string/spring, measured in Newtons (N). It represents the stiffness.
• $l_0$: Natural Length, the original length of the string/spring before any force is applied, measured in metres (m).
• $x$: Extension (or compression), the change in length from the natural length, measured in metres (m). $x = \text{stretched length} - l_0$.

Explanation

The Stretch and Squeeze Law

1. Identify the key properties: natural length ($l_0$) and modulus of elasticity ($\lambda$).
2. Determine the extension ($x$) or compression from the given lengths. Remember $x$ is the *change* in length.
3. Substitute these values into Hooke's Law, $T = \frac{\lambda x}{l_0}$, to find the tension (or thrust).
4. Use the calculated force in equations of motion ($F_{net}=ma$) or equilibrium conditions ($\Sigma F = 0$).