What does it mean when we say that the topological structure of phase space of a two-dimensional simple harmonic oscillator corresponds to a "torus"?

How many seconds does it take a pebble released from rest off a bridge to fall 29.4 m ? what is the pebble's speed when it has fallen 29.4 m ?

What is the earliest point in the universe that we can observe? why can’t we see back further than this?

25pts the diagram shows the positions of the sun, moon and earth during spring tides, when the high tides are at their highest and low tides at their lowest. what is it about these positions that causes these high and low tides?