21. how long can food that requires time-temperature control be left in the danger zone?
a. a maximum of 1 hour
b. a maximum of 2 hours
c. a maximum of 3 hours
d. a maximum of 4 hours

An electrical motor raises a 50kg load at a construct velencity .calculate the power of the motor, if it takes 40sec to raise the load through a height of 24m(take g =9.8n/g)

Fluids at rest possess no flow energy. a)- true b)- false

Compute the pressure drop of 30°c air flowing with a mean velocity of 8 m/s in a circular sheet-metal duct 300 mm in diameter and 15 m long. use a friction factor, f 0.02, and pair = 1.1644 kg/m a. 37.26 pa b. 25.27 pa n c. 29.34 pa d. 30.52 pa