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Explain the consequences of this addiction to the brain tissue

The two stars in a certain binary star system move in circular orbits. the first star, alpha, has an orbital speed of 36 km/s. the second star, beta, has an orbital speed of 12 km/s. the orbital period is 137 d. a) what is the mass of the star alpha? b) what is the mass of the star beta?

What is the force that opposes motion and works against the downward pull? a) friction b) gravity c) weight d) acceleration