Which two structures are not found in animal cells? A) vacioles and ribosomes
B) chloroplasts and ribosomes
C) cell walls and chloroplasts
D) endoplasmic reticulum and cell walls

The space between two 15-in.-long concentric cylinders is filled with glycerin (viscosity = 8.5 × 10-3 lb·s/ft2). the inner cylinder has a radius of 1 in. and the gap width between cylinders is 0.1 in. determine (a) the torque and (b) the power required to rotate the inner cylinder at 180 rev/min. the outer cylinder is fixed. assume the velocity distribution in the gap to be linear.