What is a free electron? Can someone help?

Wavelength,frequency,and energy are related.what happens to a wave as it’s wavelength gets shorter?

What is the stall speed at sea level of an airplane that weights 10000 lbs., has a wing area of 300ft^2, and a maximum lift coefficient of 1.4? what is the stall speed if flaps that double cl,max are applied?

Observations show that interstellar clouds can have almost any shape and