Why are large astronomical bodies such as planets and stars round

The diameter of a red blood cell is about 3x10^-4 inches to centimeters. for this question I wrote 7.6x10^-4cm put it was mark incorrect and i dont know why its about conversions, but the question is the following, The diameter of a red blood cell,

What is the weight, in newtons, of a 50.-kg person on the Moon?

A set of charged plates 0.00262 m apart has an electric field of 155 N/C between them. What is the potential difference between the plates? V

Which type of noise has sound at every frequency within the range of human hearing?

A 1,600 kg car traveling north at 10.0 m/s crashes into a 1,400 kg car traveling east at 15 m/s at an unexpectedly icy intersection. The cars lock together as they skid on the ice. What is their speed after the crash?

A large balloon is initially filled to a volume of 1.96 l at 318.44 k and a pressure of 2.89 atm. what volume of gas will the balloon contain at 1.77 atm and 336.33 k?

How to calculate kinetic energy? (physics/physical science)

What's the difference between the offspring of an asexual organism and a sexual organism

The contamination that results from the spread of bacteria from meat to vegetables is called

A rock has a mass of 5 kg on the moon. What is the mass of the rock on the earth