A student uses the apparatus shown in Fig. 3.1 to obtain the extension-load graph of a spring. The weights of the loads are known. The student suspends loads of increasing size from the spring and determines the different extensions produced. Fig. 3.2 is the graph the student obtains. The spring reaches its limit of proportionality when the load is 7.0N. [Figure 3.1] [Figure 3.2]

1. (a)On Fig. 3.2, sketch the shape of the graph for loads greater than 7.0N.[1]
2. (b)All the loads are removed from the spring. A block of wood is suspended from the end of the spring. The length of the spring increases from 4.9cm to 13.4cm. Determine the weight of the wooden block. weight = [2]
3. (c)The student takes a second spring that is identical to the one in Fig. 3.1 and hangs it next to the first spring. Fig. 3.3 shows a light rod passing through the rings at the lower ends of the springs. The student repeats the experiment and gradually increases the load to 9.0N. State and explain whether the limit of proportionality is reached. [Figure 3.3][2]

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