This question was well attempted by many candidates. However, few candidates did not record their observation to the required number of decimal places and in the evaluation of logarithms of numbers and this affected their graphs. Precautions were often not stated in acceptable language that is reported speech.
Part (b) was fairly attempted by most responding candidates.
In part (a) candidates were expected to:
1.read and record to 1 decimal place values of h0, D and also determine correctly four values of H = (h1–h0);
(Trend: as D decreases, H also decreases)
2. evaluate correctly to at least 3 decimal places four values of log H and log D each;
3. record data in a composite table showing D, h1, H log and log D;
4.distinguish the graph axes, select reasonable scales, plot four points correctly and draw a line that best fits the points;
5.draw a large right angled triangle on the graph line in order to determine the slope, s;
6. read ∆log H and ∆log D and also evaluate ∆log H
∆ Log D
- state any two of the following precautions in acceptable form of speech.
- Avoided parallax error in reading of the metre rule
- Avoided draught
- Ensured reading is repeated (shown on the table)
- Ensured firm clamping of the vertical metre rule
Moment of a force about a point is the product of the force and the perpendicular
distance of its line of action from the point.
(ii) Determination of the mass of metre rule
0 cm 16cm 38cm 50cm 100cm
Using the principle of moment
m (50 – 38) = 60(38 -16)
12 = 60 x 22
m = 110g.