A car travels 40 miles north in 30 minutes and then turns around and travels 20 miles south in 30 minutes. What is the cars average speed in miles/hour?

Bone-strengthening physical activity done increases bone-mineral content and bone density in youth.

Energy flows from the producer level to the level. is called

Materials will have different energies associated with the electrons inside them. this is related to how strongly bound they are by their work function. if we sandwich a material with a very low energy between two materials with a high energy, we create a trap for an electron. if this trap is very narrow in one direction in comparison to the others, this is approximately a 1-dimensional box that confines the electron. what is the lowest energy of an electron in the box if the thinnest direction across the materials is 4.81 nm?