IB Physics SL S2.3 Concluding and Evaluating Question Bank

Practise drawing conclusions from trends and uncertainty, then evaluating assumptions, random or systematic errors and realistic improvements with their predicted effects.

Exam points

state whether data support a model and cite the relevant trend, intercept or uncertainty range
identify an assumption or systematic error and predict how it biases the calculated result
propose a feasible method improvement and explain which uncertainty or limitation it reduces

Covered syllabus points

S2.3.1—Concluding S2.3.2—Evaluating

[Maximum number: 1]

A student investigates whether the Stefan-Boltzmann law, $L=4 \pi \sigma R^{2} T^{4}$ , applies to stars.
L= luminosity of the star, in W
$\sigma=$ Stefan-Boltzmann constant
R= radius of the star, in m
T= surface temperature of the star, in K
To verify the law, they obtain values from databases and manipulate the data as shown.

Table for Question S2.3 Concluding and evaluating question 1 — IB Physics SL

Outline a conclusion for the investigation.

ALTERNATIVE 1

the linear graph suggests that SB applies to stars

ALTERNATIVE 2

the «accurate » calculation of $\sigma$ from the data suggests that SB applies to stars

ALTERNATIVE 3

« if 2c has a value of $\sigma$ that is not accurate » the calculation of the $\sigma$ from the data suggests SB does not apply to stars

[Maximum number: 3]

A student studies the relationship between the centripetal force applied to an object undergoing circular motion and its period T.
The object (mass m ) is attached by a light inextensible string, through a tube, to a weight W which hangs vertically. The string is free to move through the tube. A student swings the mass in a horizontal, circular path, adjusting the period T of the motion until the radius r is constant. The radius of the circle and the mass of the object are measured and remain constant for the entire experiment.

Figure for Question S2.3 Concluding and evaluating question 2 — IB Physics SL

The student collects the measurements of T five times, for weight W. The weight is then doubled ( 2 W ) and the data collection repeated. Then it is repeated with 3 W and 4 W. The results are expected to support the relationship

W=\frac{4 \pi^{2} m r}{T^{2}}

(a)

The measurements of T were collected five times. Explain how repeated measurements of T reduced the random error in the final experimental value of m r.

[ 2 ]

(b)

Outline why repeated measurements of T would not reduce any systematic error in T. provided.

[ 1 ]

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Covered syllabus points

S2.3 Concluding and evaluating question 1

S2.3 Concluding and evaluating question 2

Question (a)

Question (b)