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Saturday, 31 October

JEE Main 2021 · PhysicsMultiple choiceSingle correctMediumMulti-step

JEE Main 31 August 2021, Shift 1, Physics Q17

Question 17 of 90 in this shift, Physics question 17 of 30, Section A.

The 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. Find the minimum escape velocity for a particle of mass 'm' to be projected from the middle of these two masses :
  1. (1)V=2G (M1+M2)rV = \frac{\sqrt{2G}\,(M_1+M_2)}{r}
  2. (2)V=122G (M1+M2)rV = \frac{1}{2}\sqrt{\frac{2G\,(M_1+M_2)}{r}}
  3. (3)V=4G (M1+M2)rV = \sqrt{\frac{4G\,(M_1+M_2)}{r}}Official answer
  4. (4)V=124G (M1+M2)rV = \frac{1}{2}\sqrt{\frac{4G\,(M_1+M_2)}{r}}

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. 25 Feb 2021, Shift 1 · Q1Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R. Assertion A : The escape velocities…EasyAssertion–reason
  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.