How long was the ice flow in the first tray? After the ice melted, how was the sand in the first tray different from the sand in the second tray?
What was the sand depth in the first tray at the beginning of the experiment? What was the sand depth at the end? Answer these questions for the second tray.
Did erosion take place in either tray? Explain your answer.
How do you think the results would change if the trays were propped up two inches?

waves moving from a fast medium to a slow medium will experience a reflection as light travels more slowly than red light. total internal reflection occurs when the critical angle is.

grav forces affect all objects magnetic forces affect magnetic objects and electric currents

it's when something is going so fast it makes a loud noise, breaking the sound barrier, for example: a jet makes a loud noise, not only cause of the jet but because they reached a point where they went so fast that you can year the noise from various parts, kinda like a police car, lets say the car was going   so fast that you hear the siren of the cop car right next to you, but the car is probably a mile a way, it's cos the siren was next to you a few seconds if you understand me