A 4.01g particle is moving at 1.36 m/s toward a stationary 9.43g particle. With what speed does the heavier particle approach the center of mass of the two partciles? i dont get how cm relates to finding speed The mass of a star like our sun is 347000 Earth masses, and the mean distance from the center of this star to the center of a planet like our Earth is 6.63*10^8 km. Treating this planet and start as particles, with each mass concentrated at its respective geometric center, how far from the center of the star is the center of mass of the planet-star system? Answer in units of km.