Why is it easier to predict where an earthquake epicenter will occur than it is to predict when it will occur?

In science and physics what is the standard unit of measure for speed?

What is an aquifer for science class

Four point charges each having charge q are located at the corners of a square having sides of length a. find symbolic expressions for the following. (a) the total electric potential at the center of the square due to the four charges (use any variable or symbol stated above along with the following as necessary: ke.) vtotal= (b) the work required to bring a fifth charge p from infinity to the center of the square (use any variable or symbol stated above along with the following as necessary: w=