Gravitational field strength
The gravitational force per unit mass exerted by a massive object on a test mass. At distance r from a point mass M, gravitational field strength g = GM/r² where G is the gravitational constant (6.67 × 10⁻¹¹ N·m²/kg²).
Formula
g = GM/r²
Real World
The Juno spacecraft, orbiting Jupiter, experiences a gravitational field strength of about 8 N/kg at its closest approach — similar to Earth's surface gravity, despite Jupiter being 318 times more massive, because Juno is still far from Jupiter's centre.
Exam Focus
Always state the direction of g (toward the centre of mass); forgetting this loses marks on 'describe' questions.
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