In this experiment you will investigate how the motion of two pendulums depends on the tension in a spring connecting them. (a) Measure and record the unstretched length $l_0$ of the coiled part of the spring as shown in Fig. 1.1. $l_0$ = \_\_\_\_\_\_ (i) Set up the apparatus as shown in Fig. 1.2. (ii) Position the stands so that the coiled part of the spring has approximate length $l_0 + 2\ \text{cm}$ (so that the spring is extended by approximately $2\ \text{cm}$). (iii)…

Physics 9702/35 — May/June 2011

Cambridge AS Level · Advanced Practical Skills · worked solutions for every part, with the mark scheme

questions

marks

120

minutes

Topics Manipulation, Measurement and Observation · Presentation of Data and Observations · Analysis, Conclusions and Evaluation

Q1Manipulation, Measurement and ObservationPresentation of Data and ObservationsAnalysis, Conclusions and EvaluationFree sample

In this experiment you will investigate how the motion of two pendulums depends on the tension in a spring connecting them.

(a)

Measure and record the unstretched length $l_0$ of the coiled part of the spring as shown in Fig. 1.1.

Fig. 1.1

$l_0$ = ______

(b)

(i)

Set up the apparatus as shown in Fig. 1.2.

Fig. 1.2

(ii)

Position the stands so that the coiled part of the spring has approximate length $l_0 + 2\ \text{cm}$ (so that the spring is extended by approximately $2\ \text{cm}$ ).

(iii)

Measure and record the length $l$ of the coiled part of the spring.
Calculate the extension $x$ of the spring, where $x = l - l_0$ .

$l$ = ______
$x$ = ______

(iv)

Gently pull bob A towards you. Release the bob and watch the movement of the two bobs.

Bob A will eventually stop and start moving again. It will then stop for a second time.

Determine and record the time $T$ between these two stops.

$T$ = ______

(c)

By moving the stands further apart, repeat (b)(iii) and (b)(iv) until you have six sets of readings of $l$ , $x$ and $T$ , with $x$ in the range $2\ \text{cm} \leq x \leq 10\ \text{cm}$ .

(d)

(i)

Plot a graph of $T$ on the $y$ -axis against $x$ on the $x$ -axis.

(ii)

Draw the straight line of best fit.

(iii)

Determine the gradient and $y$ -intercept of this line.

gradient = ______
$y$ -intercept = ______

(e)

It is suggested that the quantities $T$ and $x$ are related by the equation

T = px + q

where $p$ and $q$ are constants.

Use your answers in (d)(iii) to determine the values of $p$ and $q$ .
Give appropriate units.

$p$ = ______
$q$ = ______

(f)

Use your values in (e) to determine the extension $x$ that would be expected to give a value of $T = 75\ \text{s}$ .

$x$ = ______

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