Select the correct answer. In the context of mechanical systems, what does the term efficiency mean?

A. the factor by which a machine multiplies a force
B. the ratio of a machine’s power to the force of its input
C. the rate at which a machine performs work
D. the rate at which a machine consumes energy
E. the ratio of the work output of a machine to the work input

Afan that can provide air speeds up to 60 m/s is to be used in a low-speed wind tunnel with atmospheric air at 35 c. if one wishes to use the wind tunnel to study flat-plate boundary layer behavior up to reynolds numbes of re 10, what is the minimum plate length that should be used? at what distance from the leading edge would transition occur if the critical reynolds nurnber were rer,e = 5 × 105?