Which describes the refraction of a wave? a. waves of electromagnetic energy called x-rays pass right through skin and bones. b. light changes direction moving through the lens of a magnifying glass. c. a wave of sound bounces off a hard surface at the same angle that the wave came in.

Work = force × a. work b. energy c. distance d. momentum

Estimate the schwarzschild radius (in kilometers) for a mini-black hole formed when a superadvanced civilization decides to punish you (unfairly) by squeezing you until you become so small that you disappear inside your own event horizon. (assume that the your weight is 50 kg)

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.