Junior level Physics problem I am having trouble with: Some plans for a future space station make use of a rotational force to simulate gravity. In order to be effective the centripetal acceleration at the outer rim of the station should equal about 1g, or 98.1 m/s^2. However humans can withstand a difference of only 1/100 g between their head and feet. Assume average human height is 2 m and calculate the minimum radius for a safe effective station. (Hint: The ratio of the centripetal acceleration of astronauts feet to the centripetal acceleration of the astronauts head must be at least 99/100.) My whole class is having trouble with this problem all help appreciated.