The diagram above illustrates a uniform metre rule which is initially mounted horizontally and
symmetrically on two knife edges, L em apart with the graduated side facing upwards. When a
mass M is hung at the mid-point of the rule, it depresses it by a distance, d, which is measured on
a vertical scale.
The initial pointer position Yo, is read and the final pointer Yi after the load M has been suspended
is read and recorded. The procedure is repeated for four other values of L.
Fig. 1(a) shows the initial pointer position Yo and the final position Yi
where i = 1, 2, 4, and 5.
Fig. 1(b) represents the corresponding distances of separation L, between the knife edges
A and B where i = 1,2,4, and 5.
(i) Read and record the initial pointer position Yo and the final pointer position Yi.
(ii) Measure and record the corresponding values of Li•
(iii) Evaluate d = (Yi - Yo) and L3 in each case.
(iv) Tabulate your readings.
(v) Plot a graph of d on the vertical axis against e on the horizontal axis.
(vi) Determine the slope, s, of the graph.
2.5 x 10-13
(vii) Evaluate y = s
(viii) State two precautions that are necessary to ensure accurate results when performing this
(b)(i) State the conditions under which a number of parallel coplanar forces will be in
In the diagram above, the point G is the centre of gravity. Calculate the tension T2