A Future Use of Space Stations May Be to Provide

A future use of space stations may be to provide hospitals for severely burned persons.It is very painful for a badly burned person on Earth to lie in bed.In a space station,the effect of gravity can be reduced or even eliminated.How long should each rotation take for a doughnut-shaped hospital of 200-m radius so that persons on the outer perimeter would experience 1/10 the normal gravity of Earth?

A) 91 min
B) 8.7 min
C) 4.6 min
D) 1.5 min
E) 0.011 min