Which of the following is true for the conservation laws of matter and energy?
a. the sun plays a critical role.
b. the nitrogen cycle is a good example.
c. earth is a nearly perfect closed system.
d. the total amount of something remains the same.

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.