JEE Main · Physics ↓ Falling

Gravitation appeared 22 times across 3 years — 2.5% of Physics. This question is from Kepler's Laws of Planetary Motion.

Year 2026 2025 2024 Total
Questions 5 9 8 22

A satellite is launched into a circular orbit of radius 'R' around the earth. A second satellite is launched into an orbit of radius 1.03 R. The time period of revolution of the second satellite is larger than the first one approximately by :-

Solution & Explanation

Related Formula

By Kepler's Third Law of Planetary Motion, the square of the orbital period T is proportional to the cube of the orbital radius R:

T² = K · R³
Core Logic

Taking logs and differentiating to find fractional errors for small changes:

2 (Δ T)/(T) = 3 (Δ R)/(R) (Δ T)/(T) = (3)/(2) ((Δ R)/(R))
Step 1: Computing Percentage Change

The change in radius is Δ R = 1.03R - R = 0.03R, which means (Δ R)/(R) = 0.03 or 3%.

Substitute this into our fraction scaling relation:

(Δ T)/(T) = (3)/(2) × 0.03 = 0.045 = 4.5%
Pattern Recognition

Power factors act as direct linear multipliers for small percentage shifts. Here, the scaling factor is simply (3)/(2) times the radius change.

Chapter Mix

Class 11 Physics: Gravitation

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_2025_24_jan_morning

Practice all Gravitation previous-year questions →

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