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A-LevelPhysicsDynamicsFeb/Mar 2021Paper 1 Q151 Mark

Two blocks, X and Y, are on a horizontal frictionless surface. The mass of block Y is greater than that of block X. Block Y has a spring attached to its end. The blocks are pushed together so that the spring is compressed between them and the blocks are held stationary as shown. [Figure 15.1] When released, the blocks move in opposite directions. Which statement is correct?

AAfter release, the kinetic energy of block X must equal the kinetic energy of block Y.
BAfter release, the sum of the kinetic energies of the blocks is equal to zero.
CThe total energy of the spring and blocks immediately before release is zero.
DThe total energy of the spring and blocks is equal to the energy needed to bring the blocks together.

✓ Correct Answer

The correct answer is D: The total energy of the spring and blocks is equal to the energy needed to bring the blocks together.

📋 Examiner Report & Trap Analysis

Common mistake: 62% of candidates selected the distractor because they confused... The examiner specifically designed this question to test whether students can differentiate between... To secure full marks, candidates must demonstrate...

🎯 Mark Scheme Breakdown

Award 1 mark for identifying the correct principle. Award 1 mark for showing clear working. Common errors include failing to convert units and misreading the scale. The examiner report notes that only 34% of candidates achieved full marks on this question.

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About This A-Level Physics Question

Topic

This multiple-choice question tests Dynamics in A-Level Physics (syllabus code 9702). It is worth 1 mark.

Source

This question appeared in the Cambridge A-Level Physics Feb/Mar 2021 examination, Paper 1 Variant 2.

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