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Saturday, 31 October

JEE Main 2021 · PhysicsMultiple choiceAssertion–reasonEasyConceptual

JEE Main 25 February 2021, Shift 1, Physics Q1

Question 1 of 90 in this shift, Physics question 1 of 30, Section A.

Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R. Assertion A : The escape velocities of planet A and B are same. But A and B are of unequal mass. Reason R : The product of their mass and radius must be same. M1R1=M2R2M_1R_1 = M_2R_2 In the light of the above statements, choose the most appropriate answer from the options given below :
  1. (1)Both A and R are correct and R is the correct explanation of A
  2. (2)Both A and R are correct but R is NOT the correct explanation of A
  3. (3)A is correct but R is not correctOfficial answer
  4. (4)A is not correct but R is correct

Official answer

Option 3

NTA final key.

Chapter
Gravitation
Topic
Gravitational Potential
Idea tested
Escape Velocity and Potential Relation

Same idea in other shifts

Asked 8× in all
  1. 2 Apr 2026, Shift 2 · Q31If a body of mass 1 kg falls on the earth from infinity, it attains velocity (v) and kinetic energy (k) on reaching the surface of earth.…MediumSingle correct
  2. 4 Apr 2025, Shift 2 · Q29An object is kept at rest at a distance of 3R above the earth's surface where R is earth's radius. The minimum speed with which it must be…MediumSingle correct
  3. 6 Apr 2024, Shift 1 · Q33To project a body of mass m from earth's surface to infinity, the required kinetic energy is (assume, the radius of earth is RER_E, g =…EasySingle correct
  4. 13 Apr 2023, Shift 1 · Q36A planet having mass 9 Me and radius 4Re4R_e, where Me and Re are mass and radius of earth respectively, has escape velocity in km/s given…EasySingle correct
  5. 31 Aug 2021, Shift 1 · Q17The masses and radii of the earth and moon are (M1M_1, R1R_1) and (M2M_2, R2R_2) respectively. Their centres are at a distance 'r' apart.…MediumSingle correct
  6. 17 Mar 2021, Shift 1 · Q26The radius in kilometer to which the present radius of earth (R = 6400 km) to be compressed so that the escape velocity is increased 10…EasyNumerical value
  7. 8 Jan 2020, Shift 2 · Q22An asteroid is moving directly towards the centre of the earth. When at a distance of 10 R (R is the radius of the earth) from the earths…MediumNumerical value

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. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.