What contributions led to the acceptance of the heliocentric model of the solar system? Hurry I am timed!

Engines for propeller-driven aircraft are limited in their maximum rotational speed by the fact that the tip speed of the propeller must not approach the speed of sound in air (mach i). taking 6 ft as a typical diameter for a propeller of a light airplane and 1100 fils as the speed of sound, find the upper limit on the rpm (revolutions per minute) of the propeller shaft.

Acertain half-reaction has a standard reduction potential e_red^0 = -0.94 v. an engineer proposes using this half-reaction at the cathode of a galvanic cell that e must provide at least 1.00 v of electrical power. the cell will operate under standard conditions. a. is there a minimum standard reduction potential that the half-reaction used at the anode of this cell can have? b. is there a maximum standard reduction potential that the half-reaction used at the anode of this cell can have?

The focal length of a lens is determined by the curve of the lens and the material that the lens is made from. (5 points) is this true or false? ?