If one single-bladed propeller is turning at 570 rpm and you hear a 2.20 Hz beat when you run the second propeller, what are the two possible frequencies (in rpm) of the second propeller

Why is there friction between objects

The transfer of heat through the movement of a gas or liquid a. convection b. conduction c. radiation

Which best describes how fluids change as they travel through different portions of the convection currents? they change to solids at the outer portion of the convection currents. they change to solids at the inner portion of the convection currents. they become more dense at the outer portion of the convection currents. they become more dense at the inner portion of the convection currents