3 The press shown below has a rated load of 25 kN The twin screws have Acme threads, a diameter of 56 mm, and a pitch of 5.5 mm. Coefficients of friction are 0.05 for the threads and 0.08 for the collar bearings. Collar diameters are 88 mm. The gears have an efficiency of 95 percent and a speed ratio of 60: 1. The full-load motor speed is 1750 rev/min. a. When the motor is turned on, how fast will the press head move? b. What should be the horsepower rating of the motor? Motor Bearings Spur gears Bronze bushings Foot Worm Collar bearing

4 A double-threaded power screw with square threads pushes against a load of 3,641 N at a speed of 15 mm/s. The screw has a major diameter of 20 mm and a pitch of 3 mm. The frictional coefficient of the threads is 0.25, and collar friction is negligible. What is the rotational speed of the screw in units of revolutions per minute? Type your answer 2 points