PLEASE HELP!! Four second after starting from rest, what will be the velocity of an object in free fall?

When using the scientist method, which step comes last?

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.

Acircular ring of charge with radius b has total charge q uniformly distributed around it. what is the magnitude of the electric field at the center of the ring? 0 keq/b2 keq2/b2 keq2/b none of these answers