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Gravitation · Question 12

JEE Main 2025 (Online) 4th April Morning ShiftMCQEasy📈 Topic in 10% papers+4−1
1

Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R In the light of the above statements, choose the correct answer from the options given below

  1. A is false but R is true
  2. Both A and R are true and R is the correct explanation of A
  3. A is true but R is false
  4. Both A and R are true but R is NOT the correct explanation of A

Answer

(1) A is false but R is true

Solution

Potential energy at the surface: U = - GMmR; at infinity: U = 0.

Minimum kinetic energy needed to reach infinity: K = 0 - (- GMmR ) = GMmR

GM = gR2 K = mgR (not 12mgR) A is false.

U = - GMmr increases with r and reaches its maximum value, zero, at r R is true.

Answer: (1)

JEE Main 2025 (Online) 4th April Morning Shift

Keep practising — Gravitation

2

An 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 projected so that it does not return to earth is : (Assume M = mass of earth, G = Universal gravitational constant)

  1. 3GMR
  2. 2GMR
  3. GM2R
  4. GMR
JEE Main 2025 (Online) 4th April Evening Shift
3

Three identical spheres of mass m are placed at the vertices of an equilateral triangle of length a. When released, they interact only through gravitational force and collide after a time T = 4 seconds. If the sides of the triangle are increased to length 2a and also the masses of the spheres are made 2 m, then they will collide after seconds.

JEE Main 2025 (Online) 3rd April Morning Shift
4

A satellite of mass 1000 kg is launched to revolve around the earth in an orbit at a height of 270 km from the earth's surface. Kinetic energy of the satellite in this orbit is 1010 J. (Mass of earth = 6 1024 kg, Radius of earth = 6.4 106 m, Gravitational constant = 6.67 10-11 N m2 kg-2)

JEE Main 2025 (Online) 2nd April Evening Shift
5

Earth has mass 8 times and radius 2 times that of a planet. If the escape velocity from the earth is 11.2 km/s, the escape velocity in km/s from the planet will be:

  1. 8.4
  2. 11.2
  3. 5.6
  4. 2.8
JEE Main 2025 (Online) 28th January Evening Shift

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All JEE Main Physics chapters
Class 11Units and MeasurementsMotion in a Straight LineMotion in a PlaneLaws of MotionWork, Energy and PowerSystem of Particles and Rotational MotionGravitationMechanical Properties of SolidsMechanical Properties of FluidsThermal Properties of MatterThermodynamics (Physics)Kinetic TheoryOscillationsWaves
Class 12Electric Charges and FieldsElectrostatic Potential and CapacitanceCurrent ElectricityMoving Charges and MagnetismMagnetism and MatterElectromagnetic InductionAlternating CurrentElectromagnetic WavesRay Optics and Optical InstrumentsWave OpticsDual Nature of Radiation and MatterAtomsNucleiSemiconductor ElectronicsExperimental Skills (Physics)