University of Abuja Course: MEE 311, Theory of Machines I Time: 1 hour. Question 1 (10 marks) Test 1, 3(6)-2(3)-0 2024/2025 Session 18 Instruction: Attempt all questions. (1) State the criteria used in the classification of machines and give examples for each group. (i) Calculate the mobility of the linkages. Clearly define the number of links, number of joints (Full (lower pairs) or half (higher pairs)) 3(N-1)-232-31 2 3 5 6-9917 Leaks P A 6 627d 37 de do-₤ do T: Px d 2 Po WC Question 2.(10 marks) (i) Mention five mechanisms, machines or phenomena where friction is utilized positively. (i) A 150 mm diameter valve, against which a steam pressure of 2 MN/m² is acting, is closed by means of a square threaded screw 50 mm in external diameter with 6 mm pitch. If the coefficient of friction is 0.12; find the torque required to turn the handle. Question 3 (10 marks) 880 697 tan tank (i) What are the factors that determine the selection's belt drive to be used in a machine? (ii) Two pulleys, one 350 mm diameter and the other 150 mm diameter are on parallel shafts 1.55m apart and are connected by a crossed belt. Find the length of the belt required and the angle of contact between the belt and each pulley. What power can be transmitted by the belt when the larger pulley rotates at 200 rev/min, if the maximum permissibl tension in the belt is 1 kN, and the coefficient of friction between the belt and pulley 0.25?

Problem 4RQ: A control loop contains _______, _______, and _________.