In this experiment you will determine the mass of a metre rule. You are provided with: • a metre rule • a fixed mass taped to the rule at the 5.0 cm mark • a pivot • six 10g slotted masses • a piece of modelling clay. The fixed mass has been taped to the metre rule at the 5.0 cm mark. Do not change the position of this mass. (a) Place the pivot below the 25.0 cm mark on the metre rule, as shown in Fig. 3.1. [Figure 3.1] Place two 10g masses together to make a 20 g mass. Place the 20g mass on the metre rule and adjust the position of the mass until the rule is as close to balance as possible.

1. (a)(i)Determine the distance d of the centre of the 20 g mass from the pivot when the metre rule is as close to balance as possible. d = cm[1]
2. (a)(ii)Describe the technique you use to balance the metre rule with the 20 g mass.[1]
3. (a)(iii)Record in Table 3.1 the distance d of the centre of the mass from the pivot for mass m = 20g. Find the distance d of the centre of the mass from the pivot for values of mass m = 30g, 40g, 50 g and 60g, using the 10g masses provided. Record all values of d in Table 3.1. Calculate 1/d for each mass and record all values in Table 3.1. Give your answers to an appropriate number of significant figures. [Table 3.1][2]
4. (a)(iv)Suggest why a value of d cannot be found for mass m = 10g.[1]
5. (b)(i)Using the grid provided in Fig. 3.2 on page 11, plot a graph of 1/d on the y-axis against m on the x-axis. Start your axes from the origin (0, 0). Draw the straight line of best fit.[4]
6. (b)(ii)Calculate the gradient G of your line. Indicate on the graph the points you use. Show all your working. G =[2]
7. (b)(iii)The mass M of the metre rule can be calculated using the equation: M = 160 - 0.040 / G Use your value of G in (b)(ii) to calculate M. M = g[1]
8. (c)Remove all the 10g masses from the metre rule. Do not remove the mass fixed to the rule. You have been provided with a piece of modelling clay. Use the apparatus in (a) and your graph in (b)(i) to find the mass of the piece of modelling clay. Record any measurements you make and show your working. mass of piece of modelling clay = g[2]

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