En el artículo quinto transitorio:

The skills of analysing and interpreting are required in almost all practical activities we undertake. For example, if we were to carry out a pendulum experiment and were asked to determine how the period of the pendulum was related to the length of the pendulum, and had available a graph of the (period)2 _{against the length, we would first have to use reasoning skills to}

analyse the graph to discover what it was telling us about the period and the length. We would then have to use our mathematical skills to infer that the square of the period was proportional to the length (assuming that the graph showed no intercept and was straight). What this graph reveals does not quite answer the question as to how the period was related to the length. All we could say, judging by the graph, is that an increase in the length resulted in an increase in the period, but how much increase there would be for an increase in length by a certain factor would require us to delve into further mathematics of variation. It is only if we know how to interpret direct variation that we would be able to predict that if the length changed by a factor ‘f’, the period would change by a factor of ‘f1/2_{’). It would be clear,}

therefore, that the skills needed for analysis and interpretation are certainly more cognitive that psychomotor, certainly more on the reasoning side than on the manipulative side.

Further activities that require the use of analysis and interpretation skills will be found in

CHAPTER 37.

A useful exercise from the point of view of A/I skills and P/D skills would be to investigate how the period of a pendulum depends on the mass of the bob and a more challenging adventure would be to find out how the period depended on the radius of the bob. There would be a fair number of variables to be controlled in such exercises.

Answers to ITQs ITQ1 meter A (reads 0.5A) A 0 1 2 3 4 5 meter B (reads −0.3A) A 0 1 2 3 4 5

ITQ2 Immerse the bulb of the faulty thermometer in melting ice until the reading is steady. Note this reading. The difference between this reading and 0.0°C is the zero error at 0°C.

ITQ3 V oltage, V / V Current, I/A 0 (i) (ii) X

Examination-style questions

1 Which skills are required in doing each of the following? The first one is done for you. (i) Using no-parallax to locate an image formed by a converging lens.

[Answer: Experimental skills: handling, manipulating, observing]

(ii) Correcting the reading of a micrometer screw gauge for zero error. (iii) Measuring the length of a glass rod with a ruler.

(iv) Deciding whether to use a long pendulum or a short one to find a value for the acceleration due to gravity.

(v) Plotting the magnetic field of a bar magnet. (vi) Calculating the slope of a graph.

(vii) Timing the oscillations of a simple pendulum. (viii) Comparing the strengths of two bar magnets.

2 Your friend claims that a tennis ball will bounce higher when it is warm than it will when it is cold. Prepare a plan and a design for an investigation to decide whether your friend is right. This is a YES/NO investigation, so your design must include a hypothesis.

3 I have prepared a plan for an experiment to find the value for the acceleration of free fall (g) by allowing a pebble to fall from a tall building to the ground below. The building is about 30 m high. I have a tape 100 m long (× 0.5 cm) and a stopwatch reading to the nearest 0.01 s. The formula I hope to use to calculate the value of g is h = 1gt2

Note: all three graphs must have the same slope. This slope represents the resistance of the resistor.

• Random errors are due mainly to faulty reading of the scales of analogue instruments by the experimenter, and the faulty use of equipment.

• Systematic errors are usually zero errors in analogue instruments.

• To reduce the effect of random errors, we take an average of a large number of readings or, if a graph is drawn, we draw ‘the best line’ among the plotted points. • To remove the effect of systematic errors in a reading, we either correct the defect or

(i) State what readings I should take and show how they should be presented. (ii) Explain how I should use these readings to reach a conclusion.

(iii) State what are the likely limitations of such an experiment.

(iv) How many significant figures can I justifiably use in stating my result for g? Give a reason for your answer.

4 An experiment to determine the focal length of a converging lens was carried out, in which image distances (v) were found for six object distances (u). The values of v for u increasing and for u decreasing are shown in the table below.

(i) What do the headings ‘u increasing’ and ‘u decreasing’ convey to the reader? (ii) Copy and complete the table, expressing each value to an appropriate number of

significant figures. u/cm v/cm mean v/cm u increasing u decreasing 12.0 61.0 61.4 61.2 20.0 20.5 20.3 20.4 30.0 15.0 14.6 14.8 40.0 13.3 13.0 50.0 12.5 12.6 60.0 12.0 11.9

(iii) Given a sheet of graph paper 19 cm × 15 cm, suggest suitable scales for

u (horizontally) and v (vertically). (Hint: Consider the range of u values to be from

10 cm to 60 cm, and of v values to be from 10 cm to 65 cm.) (iv) Draw a graph of v against u.

(v) On the same axes draw the graph of the equation v = u. The values of u and v at the point where the two graphs intersect are each equal to 2f, where f represents the focal length of the lens.

Section A:





















pendulum





factors affects the period of a simple pendulum





constructing clocks

objects falling freely

objects rolling down smooth slopes

pendulums of different lengths

relationship between period and length

of pendulum

showed a revolved around Jupiter resulting in support for the heliocentric theory

of the universe move with constant

acceleration equation of motion s = ½ at2 T 2 _{varies directly as} ℓ leading to the ‘moons’ of Jupiter

and found that

KINEMATICS (or MOTION) of bodies

studied the

Galileo Galilei (1564–1642)

By the end of this chapter you should be able to:

Galileo Galilei