Why might an earthquake’s primary waves, but not its secondary waves, reach a location on the other side of the world from the epicenter?

Because the primary waves travel before the secondary waves, and therefore arrive first.

a

explanation:

no diagram was provided, but i'm guessing it's the one i've attached to my answer.

here, a mechanical force turns the rod.   this generates an electric current in the coil, which powers the bulb.

float.

archimedes' principle

denser than water sinks in water.

denser than mercury would sink in it