JEE Main · Physics ↓ Falling

Gravitation appeared 22 times across 3 years — 2.5% of Physics. This question is from Satellite Motion and Time Period.

Year 2026 2025 2024 Total
Questions 5 9 8 22

Given below are two statements : Statement I : A satellite is moving around earth in the orbit very close to the earth surface. The time period of revolution of satellite depends upon the density of earth. Statement II: The time period of revolution of the satellite is T = 2π Rₑg (for satellite very close to the earth surface), where Rₑ radius of earth and g acceleration due to gravity. In the light of the above statements, choose the correct answer from the options given below :

Solution & Explanation

Related Formula
T = 2π √((R³)/(GM)) M = ρ · (4)/(3)π R³ g = (GM)/(R²)
Core Logic

Evaluating Statement I: Substituting total mass M = ρ · (4)/(3)π R³ into time period formula:

T = 2π √((R³)/(G (ρ · (4)/(3)π R³))) = √((3π)/(G ρ))

Hence, time period depends inversely on the square root of Earth's density ρ. Statement I is true.

Evaluating Statement II: Substituting g = (GM)/(Rₑ²) into T = 2π √((Rₑ³)/(GM)):

T = 2π √((Rₑ)/(g))

Statement II is also true.

Step 1: Final Conclusion

Both Statement I and Statement II are true.

Pattern Recognition

Near-surface satellite shortcut: T = √(3π / (Gρ)) ≈ 84.6 min. Shows direct dependence on Earth's density ρ and formula T = 2π √(Rₑ / g).

Chapter Mix

Class 11 Physics: Gravitation

Reference Study Guides

More Gravitation Previous-Year Questions — Page 5

Q46 jee_main_2024_31_jan_evening Escape Velocity
The mass of the moon is 1/144 times the mass of a planet and its diameter 1/16 times the diameter of a planet. If the escape velocity on the planet is v, the escape velocity on the moon will be:
  • A. (v)/(3)
  • B. (v)/(4)
  • C. (v)/(12)
  • D. (v)/(6)

Solution

Related Formula
vescape = √((2GM)/(R))
Core Logic

For the planet: v = √((2GMₚ)/(Rₚ)) For the moon: Mm = (Mₚ)/(144) and Rm = (Rₚ)/(16).

Step 1: Setup the Ratio
vm = √((2G Mm)/(Rm)) vm = √((2G ((Mₚ)/(144)))/(((Rₚ)/(16)))) vm = √((2G Mₚ)/(Rₚ) × (16)/(144))
Step 2: Simplification
vm = √((2G Mₚ)/(Rₚ)) × √((1)/(9)) vm = v × (1)/(3) = (v)/(3)
Pattern Recognition

Escape velocity scales as √(M/R). If M scales by x and R scales by y, velocity scales by √(x/y). Here, √((1/144)/(1/16)) = √(16/144) = √(1/9) = 1/3.

Chapter Mix

Class 11 Physics: Gravitation

Q jee_main_2024_31_jan_morning Superposition Principle
Four identical particles of mass m are kept at the four corners of a square. If the gravitational force exerted on one of the masses by the other masses is ( 2√(2) + 132) Gm²L², the length of the sides of the square is
  • A. L2
  • B. 4 L
  • C. 3L
  • D. 2 L

Solution

Related Formula
F = (G m₁ m₂)/(r²)
Core Logic

Superposition Principle diagram for Q37 - JEE Main 2024 Morning
Superposition Principle diagram for Q37 - JEE Main 2024 Morning

Let the side length of the square be a. Considering one corner mass, it experiences forces from the adjacent two masses (distance a) and the diagonally opposite mass (distance √(2)a).

The forces from the two adjacent masses are at 90^° to each other:

F = (Gm²)/(a²)

The resultant of these two is √(2)F = √(2) (Gm²)/(a²), directed along the diagonal.

Step 2: Total Force Equation

The force from the diagonal mass is:

F' = Gm²(√(2)a)² = (Gm²)/(2a²)

Total resultant force Fₙₑₜ = √(2)F + F':

Fₙₑₜ = √(2) (Gm²)/(a²) + (Gm²)/(2a²) = (Gm²)/(a²) ( √(2) + (1)/(2) ) Fₙₑₜ = (Gm²)/(a²) ( 2√(2) + 12 )

Equating this to the given force value:

( 2√(2) + 132)(Gm²)/(L²) = (Gm²)/(a²) ( 2√(2) + 12 ) (1)/(32 L²) = (1)/(2 a²)

a² = 16 L² a = 4L

Chapter Mix

Class 11 Physics: Gravitation

More Gravitation Questions — jee_main_2026_22_january_evening

Practice all Gravitation previous-year questions →

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