The basis for defining the length of a day is the fact that question 21 options: a. earth moves through 365.25 days a year in its orbit about the sun. b. earth rotates on its axis in 24 hours; i. e., it rotates 15° of longitude per hour. c. earth rotates east to west. d. earth does not rotate; rather, it revolves.

Aheavy boy and a lightweight girl are balanced on a massless seesaw. the boy moves backward, increasing his distance from the pivot point. what happens to the seesaw? it is impossible to predict without knowing additional information. the side the boy is sitting on will tilt downward. the side the girl is sitting on will tilt downward. nothing; the seesaw will remain balanced.