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Saturday, 31 October

JEE Main 2021 · PhysicsMultiple choiceDiagram basedMediumDiagram reading

JEE Main 4 August 2021, Shift 2, Physics Q19

Question 19 of 90 in this shift, Physics question 19 of 30, Section A.

The potential energy function for a particle executing SHM is given by V(x)=12kx2V(x)=\frac{1}{2}kx^2, where k is the force constant of the oscillator. Which of the following diagram correctly shows the position - momentum curve for the motion.

The figure, in words

All four options are position (X) versus momentum (P) graphs; see options.
  1. (1)[figure: P versus X graph; a closed ellipse centred at the origin with an arrow on its upper right part pointing anticlockwise; labels 2mE\sqrt{2mE} at the top of the P axis with a small arrow beside it, −2mE-\sqrt{2mE} at the bottom of the P axis with a small arrow beside it, −2EK-\sqrt{\frac{2E}{K}} at the left end and 2EK\sqrt{\frac{2E}{K}} at the right end of the X axis]Official answer
  2. (2)[figure: P versus X graph; a closed ellipse centred at the origin with an arrow on its upper right part pointing anticlockwise; labels +2mE+\sqrt{2mE} at the top of the P axis and −2mE-\sqrt{2mE} at the bottom of the P axis; no labels on the X axis]
  3. (3)[figure: P versus X graph; an open arc to the right of the P axis, running from a point at height 2mE\sqrt{2mE} through the origin to a point at height −2mE-\sqrt{2mE}, with dashed lines from those two heights on the P axis to the arc ends and a dashed vertical line joining the two ends; arrows on the arc point towards the origin]
  4. (4)[figure: P versus X graph; an open arc (right half of an ellipse) from +2mE+\sqrt{2mE} on the P axis, through 2EK\sqrt{\frac{2E}{K}} on the X axis, to −2mE-\sqrt{2mE} on the P axis, with arrows pointing downwards (clockwise)]

Official answer

Option 1

NTA final key.

Same topic in other shifts

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Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. This question needs a figure we do not reproduce; it is described in words above. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.