The element copper has 29 protons. What is the atomic number of copper?

What are the differences and similarities of a compression wave and a transverse wave?

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

In which of the following cases is work being done on an object? question 2 options: pulling a trailer up a hill carrying a box down a corridor suspending a heavy weight with a strong chain pushing against a locked door