A synthetic polymer strap is installed in an industrial testing rig to study its mechanical response to cyclic loading. The top of the strap is clamped to a fixed overhead frame, and the position, yyy, of the bottom clamp below a fixed reference mark is measured.
With no tension applied, the initial position is y0=0.45 my_0 = 0.45\text{ m}y0=0.45 m.
A tensile load TTT is gradually applied up to a maximum of 120.0 N120.0\text{ N}120.0 N, and then slowly released back to zero. At each step, the position yyy is measured and the extension xxx is calculated using x=y−y0x = y - y_0x=y−y0.
The results of the test are shown in the table below:
| T / NT\text{ / N}T / N | y / my\text{ / m}y / m | x / mx\text{ / m}x / m |
|---|---|---|
| 0.0 | 0.45 | 0.00 |
| 30.0 | 0.62 | 0.17 |
| 60.0 | 0.81 | 0.36 |
| 90.0 | 1.05 | 0.60 |
| 120.0 | 1.38 | [B]\textbf{[B]}[B] |
| 90.0 | 1.22 | 0.77 |
| 60.0 | 1.01 | 0.56 |
| 30.0 | 0.76 | 0.31 |
| 0.0 | 0.58 | 0.13 |
Determine the missing value of the extension, [B]\textbf{[B]}[B], at a tension of 120.0 N120.0\text{ N}120.0 N.
State and explain whether the strap obeys Hooke's law during the loading phase.
In a graph of tension TTT against extension xxx, the loading and unloading curves form a closed loop.
15 exam-style questions on OCR A A Level Physics Materials, covering Springs and Mechanical properties of matter. Each one has a worked solution and a mark scheme showing where the marks go.