Measuring the **elasticity** of materials

### Simulation

Mass & Springs (PhET Simulation)

### Time for Practice

- A rope can be considered as a spring with a very high spring constant \begin{align*}k,\end{align*}so high, in fact, that you don’t notice the rope stretch at all before it “pulls back.”
- What is the \begin{align*}k\end{align*} of a rope that stretches by \begin{align*}1\;\mathrm{mm}\end{align*} when a \begin{align*}100\;\mathrm{kg}\end{align*} weight hangs from it?
- If a boy of \begin{align*}50\;\mathrm{kg}\end{align*} hangs from the rope, how far will it stretch?

#### Answers to Selected Problems

- a. \begin{align*}9.8 \times 10^5 \;\mathrm{N/m}\end{align*} b. \begin{align*}0.5 \;\mathrm{mm}\end{align*}