What are the advantages of laser communications? A. Lasers can be switched on and off at high speeds
B. Laser light remains collimated (focused) over long distances
C. Lasers are the lowest cost method for communicating over long distances
D. The much shorter wavelengths allow for more data to be transmitted per second

Amixture of slurry and mud is to be pumped through a horizontal pipe of diameter 500 mm. the fluid behaves as a bingham plastic with a yield stress of 30 pa and viscosity 0.04 pa.s. describe the effects of the shear stress through a transverse section of the pipe by plotting the variation in shear stress and velocity profile: (i) just before the slurry starts to move (ii) as the slurry flows when the pressure gradient is double that in part (i)