Physics Paper 1, May/June. 2011
 Questions: 1 2 3 4 5 6 Main
Weakness/Remedies
Strength

Alternative a
Question 1

(a)  Diagram

You are provided with a wooden block to which a hook is fixed, set of masses, spring
balance and other necessary materials.

Using the diagram above as a guide, carry out the following instructions.

1. Record the mass mo indicated on the wooden block
2. Place the block on the table.
3. Attach the spring balance to the hook
4. Pull the spring balance horizontally with a gradual increase in force until the block just starts to move.  Record the spring balance reading F.
5. Repeat the procedure by placing in turn mass m = 200, 400, 600 and 800 g on top of the block.  In each case, read and record the corresponding value of F.
6. Evaluate M = mo + m and R =  in each case.
8. Plot a graph with F on the vertical axis and R on the horizontal axis.
9. Determine the slope, s, of the graph.
10. State two precautions taken to ensure accurate results.

(b)    (i)   Define coefficient of static friction.                                                               [2 marks]
(ii)   A block of wood of mass 0.5 kg is pulled
horizontally on a table by a force of 2.5 N
Calculate the coefficient of static friction
between the two surfaces. (g = 10ms-2)                                             [2 marks]
This question on the laws of solid friction was very

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Observation

This question on the laws of solid friction was very popular among the candidates.  It was well attempted by most responding candidates.  Under observation, candidates missed the unit of R which is Newton (N) as they recorded it in grammes(g)

Plotting of the graph and determination of slope were however well handled by most  candidates. The precautions were not properly stated by most candidates. In the part b, most candidates were unable to define correctly the coefficient of static friction but they were able to use formular to calculate the co-efficient of static friction between two surfaces.

The demands of part (a) include the following:

-    measurement of and recording of mo, M and F
-    evaluation of M = (mo + M) and R =
-     data should be recorded in composite table and in trend
(Trend: As m increases, F increases)
-     The graph axes should be indictated and reasonable scales selected to plot four
points required;
-     determination of the slope using large right angled triangle on the graph line.
-     state any two of the following precautions in acceptable speech:
-    Avoided parallax error in reading spring balance
-    Tapped the wood/load slightly to avoid sticking to the table
-    Repeated readings shown on table.

(b)(i)   Definition of the term coefficient of static friction
This is the ratio of the frictional force F (when the body is just about to move) to the normal  reaction R (Between the two surfaces in contact).

(ii)   U= F/R

= 2.5/5

=   0.5