Quick questions on Physical quantities and units: SI units, homogeneity and uncertainty - CCEA A-Level Physics

5short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.

What are homogeneity of equations?

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For example, in

v = u + at

each term has units of

\text{m s}^{-1}

, so the equation is homogeneous and could be correct.

What are uncertainties?

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The absolute uncertainty is the

\pm

range on a single measurement, often taken as half the smallest scale division or the spread of repeated readings.

What is q1?

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Show that the unit of energy, the joule, is equivalent to

\text{kg m}^2\,\text{s}^{-2}

. [2 marks]

What is q2?

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A length is measured as

0.250\ \text{m}

with an absolute uncertainty of

0.005\ \text{m}

. State its percentage uncertainty. [1 mark]

What is q3?

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A current of

0.50\ \text{A} \pm 2\%

flows through a resistor of

12\ \Omega \pm 3\%

. Find the percentage uncertainty in the power dissipated, given

P = I^2 R

. [2 marks]

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