Gravitation

chaptermedium71 MCQ

Universal law, gravitational field, potential, satellites and Kepler's laws.

Practice 10 questions Back to syllabus~15 min · 71 questions in the bank

What is Gravitation?

Every particle attracts every other with F = G m1 m2 / r², where G = 6.67 x 10^-11 N m²/kg²

Key formula / rule: Universal law and escape speed

Key points

Apply the universal law, the variation of g, and Kepler's laws to planets and satellites

Common exam trap

Using U = mgh over distances comparable to the earth's radius

Definitions

Name: Universal law of gravitation
Definition: Every particle attracts every other with F = G m1 m2 / r², where G = 6.67 x 10^-11 N m²/kg²

Name: Key idea
Definition: Gravitational potential energy is U = -G M m / r, zero at ∞; for a circular orbit gravity supplies exactly the centripetal force

Name: Exam insight
Definition: Escape speed is 11.2 km/s and is independent of the escaping body's mass; a near-earth orbital speed is about 7.9 km/s

Name: Worked example
Definition: Satellite at height h: v = sqrt(GM/(R + h)), which reduces to √(gR) for h much less than R

Learning objectives

Apply the universal law, the variation of g, and Kepler's laws to planets and satellites

Formulae

Name: Universal law and escape speed
Expression: F = G m1 m2 / r²; v_e = √(2 G M / R)

Name: Kepler's third law
Expression: T² proportional to a³

Common mistakes

Using U = mgh over distances comparable to the earth's radius
Confusing orbital speed with escape speed

Keywords

gravitation
universal law
kepler
orbit
satellite
escape speed
acceleration due to gravity

Practice 10 questions