A fan uses a rotating blade to moves 2m3 of air each second at a speed of 3 m/s. Assumes air is initially at rest and has a density of 1 kg/m3. Fans are inefficient; assume an efficiency of 10%. What is the acceleration of the air? 

If a clock aboard a space ship traveling at 0.900 c of the speed of light relative to earth chimes once at the beginning of the hour and again when it reads one hour later, how much time would an observer on earth say elapsed between the two chimes?

Which is the correct symbol for an isotope of iodine with 53 protons and 78 neutrons?

Awind turbine is rotating counterclockwise at 0.5 rev/s and slows to a stop in 10 s. its blades are 20 m in length. (a) what is the angular acceleration of the turbine? (b) what is the centripetal acceleration of the tip of the blades at t=0s? (c) what is the magnitude and direction of the total linear acceleration of the tip of the blades at t=0s?