A student suspends a spring from a support. He attaches different loads to the lower end of the spring. For each load attached, he measures the extension of the spring. Fig. 3.1 shows the extension–load graph obtained. [Figure 3.1 (extension-load graph)]

1. (a)The extension of the spring is directly proportional to the load. State the two features of the graph that show this. 1. ............................................................................................................................................................................ 2. ............................................................................................................................................................................ [2][2]
2. (b)Describe how the student can show that the spring reaches its limit of proportionality at 8.0 N. ............................................................................................................................................................................. ............................................................................................................................................................................. ............................................................................................................................................................................. ............................................................................................................................................................................. [2][2]
3. (c)The spring is used in a simple device known as an accelerometer, shown in Fig. 3.2. [Figure 3.2 (accelerometer with 5.0 kg mass, spring, smooth surface, and direction of acceleration)] The spring is fixed at one end and attached to a mass of 5.0 kg at the other end. The mass rests on a smooth, horizontal surface. There is no friction between the mass and the surface. The whole device is placed in a car. The car accelerates and the student notices that the extension of the spring is 3.0 cm. Using Fig. 3.1, calculate the acceleration of the car. acceleration = ..................................................... [3][3]

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