Alternative A
Question 1A
You are provided with a metre rule, a knife edge, set of masses, inextensible string, retort support and other necessary apparatus.
- Place the metre rule on the knife edge. Read and record the point G, where the metre rule balances horizonatally, as shown in Fig 1 (a).
- Suspend the metre rule at G with the aid of the string provided and attach the string to the retort support as shown in Fig 1 (b). Keep the string attached to this point throughout the experiment.
- Attach the mass M0 at the 80cm mark of the metre rule. Determine the distance y of M0 from G. Keep M0at this position throughout the experiment.
- Suspend a mass M=40g on the side AG and adjust its position until the metre rule balances horizontally.
- Measure and record the distance x of M from G. Evaluate x-1.
- Repeat the procedure for four other values of M=60g, 80g, 100g and 120g.
Measure and record x and evaluate x-1 in each case.
- Tabulate the readings.
- Plot a graph of M on the vertical axis and x-1 on the horizontal axis, starting both axes from the origin (0,0).
- Determine the slope, s, of the graph.
- Given that s=y M0, determine M0.
- State two precautions taken to obtain accurate results.
Observation
Part (a) Candidates performance was satisfactory. Many candidates were able to attempt the question satisfactorily. However, few candidates could not obtain correct graph because they mistakenly converted the value such as 0.027 to 27 x 10-3 which made the plotting of graph and determination of slope incorrect.
1. (a) OBSERVATIONS
(i) Position of G = 50.0 ± 0.5 cm correctly recorded
(ii) Value of y correctly recorded to at least 1 d.p in cm (y = 80 – G)
(iii) Five values of m correctly recorded in grammes
(iv) Five values of x correctly recordedto at least 1 d.p. in cm and in trend.
(Trend: As m increases, x decreases)
(Deduct 1 mark for each wrong or missing value)
(v) Five values of x-1 correctly evaluated to at least 3 d.p.
(Deduct ½ mark for each wrong or missing value)
(vi) Composite table showing at least m, x and x-1.
Note: Value of x less than G
GRAPH [06]
(i) Both axes correctly distinguished (Award ½ mark each)
(ii) Reasonable Scales (Award ½ mark each)
(iii) Five points correctly plotted
(Deduct 1 mark for each wrong or missing point)
(iv) Line of best fit
Note: If graph does not start from origin (0,0) deduct 1 mark for d.i.
SLOPE (s) (02)
(i) Large right-angled triangle
(ii) Dm correctly determined
(iii) Dx-1 correctly determined
(iv) 
correctly evaluated
DETERMINATION OF M0 [01]
s = yM0
M0 = 
Correct substitution
Correct Arithmetic
PRECAUTIONS [02]
Award 1 mark for any 2 correct precautions stated in acceptable tense.
- Avoided parallax error in reading metre rule
- Noted/corrected/Avoided zero error on metre rule
- Avoided draught
- Ensured that support was rigid/firm
- Repeated readings shown on table
- Ensured mass does not touch or rest on table