The human head weighs 4.8 kg and its center of mas 1.8 cm in front of the spinal column joint. If the trapezius muscle inserts 1.1 cm behind the spinal cord joint, how much downward force does it need to exert in order to maintain equilibrium

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?