Why aren’t descriptive investigations repeatable

What is hidden during a lunar eclipse? isn't the moon hidden?

When you push downward on a book at rest on a table, you feel an upward force. does this force depend on friction? defend your answer.

Complete these sentences. if a roller coaster train has a potential energy of 1,500 j and a kinetic energy of 500 j as it starts to travel downhill, its total energy isj. once the roller coaster train gets closer to the bottom of the hill, its kinetic energy increases to 1,100 j, and its potential energy decreases to j. when the train reaches the bottom of the track and is traveling along the ground, its kinetic energy isj.