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Saturday, 31 October

JEE Main 2021 · PhysicsMultiple choiceDiagram basedMediumData or graph

JEE Main 18 March 2021, Shift 2, Physics Q3

Question 3 of 90 in this shift, Physics question 3 of 30, Section A.

A particle of mass m moves in a circular orbit under the central potential field, U(r)=−CrU(r) = -\frac{C}{r}, where C is a positive constant. The correct radius –velocity graph of the particle’s motion is :

The figure, in words

All four options are graphs of r (vertical axis) against v (horizontal axis), origin labelled O.
  1. (1)[figure: graph of r (vertical) vs v (horizontal) with origin O; curve starts at the origin tangent to the v axis and rises with increasing steepness toward the upper right]
  2. (2)[figure: graph of r vs v; straight line from the origin rising to the upper right]
  3. (3)[figure: graph of r vs v; decreasing curve starting high near the r axis and flattening toward the v axis as v increases, not touching the origin]Official answer
  4. (4)[figure: graph of r vs v; curve starting at a point on the r axis, bending downward like a quarter circle arc and ending on the v axis]

Official answer

Option 3

NTA final key.

Chapter
Gravitation
Topic
Orbital Mechanics
Idea tested
Orbital Velocity

Same idea in other shifts

Asked 6× in all
  1. 8 Apr 2024, Shift 2 · Q36Two satellite A and B go round a planet in circular orbits having radii 4R and R respectively. If the speed of A is 3v3v, the speed of B…EasySingle correct
  2. 10 Apr 2023, Shift 1 · Q34Two satellites of masses mm and 3m3m revolve around the earth in circular orbits of radii rr & 3 r3\,r respectively. The ratio of orbital…EasySingle correct
  3. 12 Apr 2023, Shift 1 · Q31Two satellites A and B move round the earth in the same orbit. The mass of A is twice the mass of B. The quantity which is same for the…EasySingle correct
  4. 25 Jun 2022, Shift 2 · Q55Two satellites S1S_1 and S2S_2 are revolving in circular orbits around a planet with radius R1R_1= 3200 km and R2R_2= 800 km respectively.…EasyNumerical value
  5. 4 Sep 2020, Shift 2 · Q6A body is moving in a low circular orbit about a planet of mass M and radius R. The radius of the orbit can be taken to be R itself. Then…EasySingle correct

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.