How many hours of sleep do kids/teens need

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According to Johns Hopkins pediatrician Michael Crocetti, M.D., M.P.H. , teens need 9 to 9½ hours of sleep per night—that's an hour or so more than they needed at age 10.

the gravitational force on an object increase as the mass of an object also, im not going to report you, but this question should be under the science category, not health