Gravitation: Advanced — Dark Matter MCQ

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Advanced — Dark MatterHardQuestion 30773

Question

Galaxy rotation curves (stars orbiting galaxy centres at nearly constant speed for all radii) suggest:

A
Newtonian gravity breaks down at galactic scales
B
There is unseen dark matter providing extra gravitational mass
Correct
C
Stars orbit by electrostatic forces
D
Kepler's laws don't apply beyond the solar system

Correct answer

There is unseen dark matter providing extra gravitational mass

Explanation

Kepler/Newton predict v ∝ 1/√r for orbital speed beyond a galaxy's visible mass. Observations show v ≈ constant (flat rotation curve), implying much more mass (dark matter) than visible matter exists.

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