Gravitation – Board Exam Numericals

Stage 2 • Page 3 • Solved Numerical Problems


Numerical 1: Calculate the gravitational force between two masses of 5 kg and 10 kg separated by 2 m.

Given:

  • m1 = 5 kg
  • m2 = 10 kg
  • r = 2 m
  • G = 6.67 × 10−11 N m² kg−2

Formula:

F = G (m1 m2) / r²

Substitution:

F = 6.67 × 10−11 × (5 × 10) / 2²

Calculation:

F = 8.34 × 10−10 N

Answer: Gravitational force = 8.34 × 10−10 N


Numerical 2: Find the weight of a body of mass 60 kg on Earth.

Given:

  • m = 60 kg
  • g = 9.8 m/s²

Formula:

W = mg

Substitution:

W = 60 × 9.8

Answer:

W = 588 N


Numerical 3: Calculate acceleration due to gravity on a planet whose mass is twice that of Earth and radius is twice Earth’s radius.

Using:

g = GM / R²

For the planet:

  • M′ = 2M
  • R′ = 2R

g′ = G(2M)/(2R)² = 2GM / 4R²

g′ = g / 2

Answer: Acceleration due to gravity becomes half of Earth’s value.


Numerical 4: Calculate escape velocity from Earth (Given g = 9.8 m/s², R = 6.4 × 106 m).

Formula:

ve = √(2gR)

Substitution:

ve = √(2 × 9.8 × 6.4 × 106)

Answer:

ve ≈ 11.2 km/s


Numerical 5: A body weighs 490 N on Earth. What is its mass?

Given:

  • W = 490 N
  • g = 9.8 m/s²

Formula:

m = W / g

Calculation:

m = 490 / 9.8 = 50 kg


Board Exam Tips for Numericals

  • Write Given → Formula → Substitution → Answer
  • Always include units
  • Box final answers
  • Avoid skipping steps
  • Use g = 9.8 unless stated otherwise

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