Working as a Physicist | Edexcel A-Level Physics (9PH0)
Working as a Physicist
- 82 questions
- 7 subtopics
- Topic 1, examined on all three papers
- Paper 1, Paper 2 and Paper 3
Runs through the whole course rather than sitting in one paper: SI units and whether an equation is homogeneous, the difference between random and systematic error, how uncertainties are estimated and combined, and how a result is judged against an accepted value.
It also covers peer review and how scientific evidence is used in public decisions.
Sample questions from Working as a Physicist
Answer each one closed book first, then open the answer.
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SI base units, derived units and homogeneity
What is the newton expressed in SI base units?
Show the answer
Since force is mass times acceleration, 1 N = 1 kg m s⁻². -
SI base units, derived units and homogeneity
The spring constant k is force divided by extension, so what are its SI base units?
Show the answer
Its unit is N m⁻¹, which in base units is kg s⁻². -
Unit prefixes, conversion and order-of-magnitude estimates
Why should the result of an estimate normally be quoted to one significant figure?
Show the answer
The input values are only roughly known, so further figures would imply a precision the estimate does not have. -
Unit prefixes, conversion and order-of-magnitude estimates
What does the symbol ∝ mean in a relationship such as F ∝ Δp/Δt?
Show the answer
It means 'is directly proportional to', so doubling the rate of change of momentum doubles the force; the relationship becomes an equation F = kΔp/Δt, and in SI units k = 1. -
Resolution, random errors and systematic errors
How can the effect of random error on a result be reduced?
Show the answer
Repeat the measurement several times and take the mean, since random deviations above and below the true value tend to cancel. -
Resolution, random errors and systematic errors
What is the difference between the accuracy and the precision of a set of measurements?
Show the answer
Accuracy describes how close the readings are to the true value, while precision describes how closely repeated readings agree with one another. -
Uncertainty and how uncertainties combine
How is the uncertainty in a reading from a digital meter usually taken?
Show the answer
It is taken as plus or minus the last displayed digit, which is the resolution of the instrument. -
Uncertainty and how uncertainties combine
How are uncertainties combined when two quantities are multiplied or divided?
Show the answer
Their percentage uncertainties are added.
The 7 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| SI base units, derived units and homogeneity | Recall questions on the six base quantities, how a derived unit is built from them, and why a homogeneity check can rule an equation out but never prove it right. | 11 |
| Unit prefixes, conversion and order-of-magnitude estimates | Recall questions on the prefixes from pico to tera, converting to SI before substituting, and making an order-of-magnitude estimate to one significant figure. | 18 |
| Resolution, random errors and systematic errors | Recall questions on the resolution of a rule, calliper and micrometer, the difference between random and systematic error, zero errors, and accuracy against precision. | 9 |
| Uncertainty and how uncertainties combine | Recall questions on estimating uncertainty from an analogue scale, a digital meter and repeated readings, and on adding absolute or percentage uncertainties. | 8 |
| Improving measurements, graphs and evaluating results | Recall questions on timing several swings, parallax, light gates, error bars, anomalous results, significant figures, and deciding whether a result agrees with an accepted value. | 13 |
| Peer review, publication and scientific integrity | Recall questions on what a peer reviewer checks, why a method must be reproducible, the two forms of misconduct, and why funding is declared. | 8 |
| Risk, benefit and the role of science in society | Recall questions on hazard against risk, why perceived risk differs from measured risk, and why science can inform a policy decision but not make it. | 15 |
How the guide is worked
Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.
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Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
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Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
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Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.
Read the full method, the return schedule and the research behind it.
Nearby topics
Edexcel A-Level Physics Active Recall Guide
Every topic, not just this one. 1,616 questions with their answers.