A student suspends a spring from a clamp stand. He measures the unstretched length of the spring with no load attached. He then attaches different loads to the lower end of the spring and measures the new lengths of the spring. Fig. 1.1 shows how the total length of the spring depends on the load attached. [Figure 1.1]

1. (a)At point P on Fig. 1.1, the line stops being straight and begins to curve. State the name of point P.[1]
2. (b)(i)Using Fig. 1.1, determine the unstretched length of the spring.[1]
3. (b)(ii)Calculate the extension of the spring for a load of 4.0N.[1]
4. (c)The student attaches a small block of wood to an identical spring. The extension of the spring is 2.7 cm. The gravitational field strength g is 10N/kg. Calculate the mass of the block of wood.[2]

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