A student investigates the stretching of a spring by hanging weights from it.
The student measures and records the unstretched length l0 l_0\,l0 of the spring (not including the loops at the ends) as 3.2 cm when the load on the spring is F=0.00 NF = 0.00\text{ N}F=0.00 N. Describe one technique that can be used to obtain an accurate value for l0l_0l0.
The student suspends various loads F F\,F from the spring, measures the new length lll, and calculates the extension e=l−l0e = l - l_0e=l−l0. The results are shown in Table 1.1.
Calculate the extension e e\,e of the spring when F=7.50 NF = 7.50\text{ N}F=7.50 N and complete Table 1.1.
Table 1.1
| F/NF / \text{N}F/N | l/cml / \text{cm}l/cm | e/cme / \text{cm}e/cm |
|---|---|---|
| 0.00 | 3.2 | 0.0 |
| 1.50 | 6.8 | 3.6 |
| 3.00 | 10.5 | 7.3 |
| 4.50 | 14.1 | 10.9 |
| 6.00 | 17.6 | 14.4 |
| 7.50 | 21.3 | [ ] |
Plot a graph of F/NF / \text{N}F/N (yyy-axis) against e/cme / \text{cm}e/cm (xxx-axis). Start both axes from the origin (0,0)(0,0)(0,0) and draw a straight line of best fit.
Determine the gradient G G\,G of your graph. Show your working clearly.
The spring constant k k\,k is numerically equal to the gradient GGG. Record the value of k k\,k to a suitable number of significant figures with its unit.
245 exam-style questions on CIE IGCSE Physics 1.5 Forces, covering 1.5.1a Forces, resultant force and motion, 1.5.1b Load–extension graphs and the spring constant, 1.5.1c Friction and drag, 1.5.1d Force, mass and acceleration, 1.5.1e Motion in a circular path, 1.5.2a Moment of a force, 1.5.2b Principle of moments and equilibrium, and 1.5.3 Centre of gravity and stability. Each one has a worked solution and a mark scheme showing where the marks go.