In this experiment you will investigate the balancing of a loaded metre rule. You are provided with: • a metre rule with a load of mass M fixed to it • a pivot • a set of 10g slotted masses. The position of the load has been fixed, with its centre directly above the 5.0cm mark. Do not attempt to adjust the position of the fixed load during the experiment.

1. (a)• Place the pivot under the 50.0cm mark of the rule. • Using the 10g slotted masses, place another load of mass m = 50g on the rule. • Adjust the position of the load of mass m = 50g until the rule is as close to balanced as possible as shown in Fig. 3.1. [Figure 3.1] Measure and record, to the nearest 0.1 cm, the distance d from the centre of the 50g mass to the 50.0 cm mark on the rule when the rule is balanced. d = .................................................... cm[1]
2. (b)It is difficult to balance the rule exactly. Describe the technique you use to make sure that your value of d is as accurate as possible.[1]
3. (c)(i)Repeat (a) for values of mass m from 60 g to 100 g. Record all your readings in Table 3.1. Include your readings from (a). [Table 3.1][2]
4. (c)(ii)Calculate the value of 1000/d for each value of d. Record your values of 1000/d in Table 3.1 to an appropriate number of significant figures for this experiment.[2]
5. (d)On the grid provided in Fig. 3.2 on page 11, plot a graph of m on the y-axis against 1000/d on the x-axis. The axes do not need to start from the origin (0, 0). Draw the straight line of best fit.[4]
6. (e)Calculate the gradient G of your line. Show all working and indicate on the graph the values you use.[2]
7. (f)The mass M of the load fixed to the rule can be determined using the equation: M = 22.2 x G Use your value of G from (e) to calculate the mass M of the load fixed to the rule. mass M = .................................................... g[1]
8. (g)Suggest why this method of determining the mass M of the load fixed to the rule is unsuitable if a movable load of mass m = 40g is used.[1]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.