When drilling a well at constant angular velocity, the bottom end of the drill pipe encounters a torsional resistance ta. also, soil along the sides of the pipe creates a distributed frictional torque along its length, varying uniformly from zero at the surface b to ta at a. determine the minimum torque tb that must be applied by the drive unit to overcome the resisting torques, and calculate the maximum shear stress in the pipe. the pipe has an outer radius ro and an inner radius ri.

You have two photos of a person walking. one shows the person at the corner of third and main streets, the other shows the person at the corner of tenth and main streets. there are lampposts at every corner in this town, and the first picture shows it to be 10: 32: 00 exactly. the second picture shows it to be 10: 49: 30. you know three facts: (1) all of the clocks are synchronized; (2) there are exactly 12 equal-sized blocks per kilometer in this town; and (3) the streets that cross main in this area are numbered consecutively, with no interruptions. what is the person’s average speed in kilometers per hour?