A student investigates the balancing of a metre rule. She uses a metre rule that has a small hole drilled through it at the $5.0\text{ cm}$ mark. - She pivots the rule at the $5.0\text{ cm}$ mark. - She supports the other end of the rule using a newton meter attached to a loop of string placed at the $95.0\text{ cm}$ mark. - She suspends a $200\text{ g}$ mass from the rule using a loop of thread. - The student moves the loop of thread supporting the $200\text{ g}$ mass until…

Physics 5054/42 — October/November 2020

Cambridge O-Level · Alternative to Practical · worked solutions for every part, with the mark scheme

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Topics Experimental Contexts · Analysis, Conclusions and Evaluation · Observations and Measurements · Use of Techniques, Apparatus and Materials · Planning Experiments and Investigations

Q114MExperimental ContextsObservations and MeasurementsAnalysis, Conclusions and EvaluationUse of Techniques, Apparatus and MaterialsFree sample

A student investigates the balancing of a metre rule.

She uses a metre rule that has a small hole drilled through it at the $5.0\text{ cm}$ mark.

She pivots the rule at the $5.0\text{ cm}$ mark.
She supports the other end of the rule using a newton meter attached to a loop of string placed at the $95.0\text{ cm}$ mark.
She suspends a $200\text{ g}$ mass from the rule using a loop of thread.
The student moves the loop of thread supporting the $200\text{ g}$ mass until it is at the $25.0\text{ cm}$ mark on the metre rule.

Fig. 1.1 shows the apparatus set up by the student.

Fig. 1.1

She calculates the distance $d$ of the mass from the pivot and records her value in the first row of Table 1.1.
She adjusts the height of the clamp supporting the newton meter until the rule is horizontal.
She records the reading $F$ on the newton meter in the first row of Table 1.1.
The student repeats this procedure with the loop of thread supporting the mass at the $40.0\text{ cm}$ , $55.0\text{ cm}$ , $65.0\text{ cm}$ and $80.0\text{ cm}$ marks on the metre rule.

Table 1.1

reading on rule / $\text{cm}$	distance $d$ from pivot / $\text{cm}$	newton meter reading $F$ / $\text{N}$
25.0	20.0	1.1
40.0	35.0	1.4
55.0
65.0	60.0	2.0
80.0	75.0	2.3

(a)

Fig. 1.2 shows the newton meter reading when the $200\text{ g}$ mass is placed at the $55.0\text{ cm}$ mark on the metre rule.

Fig. 1.2

(i)

In Table 1.1, record the distance $d$ of the mass from the pivot.

(ii)

In Table 1.1, record the reading $F$ on the newton meter.

(b)

On Fig. 1.3, plot a graph of $F$ on the $y$ -axis against $d$ on the $x$ -axis. Start both axes from the origin. Draw the straight line of best fit.

Fig. 1.3

(c)

(i)

Calculate the gradient $m$ of your line.

Show all working and indicate on the graph the values you choose.

$m$ = ______ $\text{N/cm}$

(ii)

Extend your line so that it cuts the $y$ -axis. Write down the intercept $c$ that your line makes with the $y$ -axis.

$c$ = ______ $\text{N}$

(iii)

Calculate $w$ , where

w = \frac{c}{m}

$w$ = ______ $\text{cm}$

(iv)

The weight $W$ of the metre rule is given by the equation shown

W = \frac{w}{k}

where $k = 22.5\text{ cm/N}$ .

Calculate $W$ . Give your answer to an appropriate number of significant figures.

$W$ = ______ $\text{N}$

(d)

(i)

When performing the investigation, the student rests a spirit level on the rule to check that the rule is horizontal before taking each newton meter reading.

Suggest why using a spirit level in this way is not suitable for carrying out the check in this instance.

(ii)

Describe a method, other than using a spirit level, of checking that the rule is horizontal.

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3 more questions

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Q3Use of Techniques, Apparatus and Materials · Experimental Contexts · Analysis, Conclusions and Evaluation6M
Q4Observations and Measurements · Experimental Contexts · Use of Techniques, Apparatus and Materials · Analysis, Conclusions and Evaluation · Planning Experiments and Investigations4M

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