12. a 0.5 kg ball traveling at 6.2 m/s collides head-on with a 1.0 kg ball traveling in the
opposite direction at a speed of 12.0 m/s. after the collision, the 0.5 kg ball rebounds at
a speed of -14.0 m/s. what is the final speed of the 1.0 kg ball?

The sun’s mass is 2.0×10^ 30 kg, its radius is 7.0×10 5 km, and it has a rotational period of approximately 28 days. if the sun should collapse into a white dwarf of radius 3.5×10 3 km, what would its period be if no mass were ejected and a sphere of uniform density can model the sun both before and after?