9702 · 1.1
Physical quantities flashcards
Revision flashcards for Cambridge 9702 Physical quantities (syllabus 1.1). Flip, recall, then mark a real past-paper question.
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What defines a physical quantity?
A numerical value and an associated unit.
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List three SI base quantities and their units.
Mass (kilogram, kg), Length (meter, m), Time (second, s).
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What is a derived unit? Give an example.
A unit formed by combining base units, e.g., the Newton (N) for force (kg m s⁻²).
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What does 'dimensional homogeneity' mean for an equation?
The units on both sides of the equation must be consistent (the same).
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What is the key difference between a scalar and a vector quantity?
A scalar has only magnitude (e.g., mass, speed), while a vector has both magnitude and direction (e.g., force, velocity).
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How do you resolve a vector V into its component adjacent to angle $\theta$?
V_x = V \cos \theta
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What is the difference between accuracy and precision in measurements?
Accuracy is how close a measurement is to the true value; precision is how close repeated measurements are to each other.
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How can random errors be reduced?
By taking multiple readings and calculating an average, or using more precise equipment.
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What is a systematic error, and how might it be reduced?
A consistent deviation from the true value (e.g., zero error); reduce it by calibrating instruments or correcting for background.
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How do you calculate the absolute uncertainty for a single reading on an instrument?
It's typically \pm half of the smallest division on the instrument scale.
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When adding or subtracting quantities, how are their uncertainties combined?
You add their absolute uncertainties.
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When multiplying or dividing quantities, how are their uncertainties combined?
You add their percentage uncertainties.