Name two things that are used to machines be more efficient

What are similarities and differences of reflection, refraction, diffraction and absorption?

Tall pacific coast redwood trees can reach heights of about 100 m. if air drag is negligibly small, how fast is a sequola cone moving when it reaches the ground f it dropped from the top of a 100 m tree?

What is the temperature in degrees celsius of a substance with a tempature of 49k