Engineering Answers

A manufacturing company produces bearings. One line of bearings is specified to be 1.64 centimeters (cm) in diameter. A major customer requires that the variance of the bearings be no more than 0.001 cm2. The producer is required to test the bearings before they are shipped, and so the diameters of 16 bearings are measured with a precise instrument, resulting in the following values: 1.69 1.62 1.63 1.70 1.66 1.63 1.65 1.71 1.64 1.69 1.57 1.64 1.59 1.66 1.63 1.65 Assume bearing diameters are normally distributed. Use the data and α = 0.025 to test the data to determine whether the population of these bearings is to be rejected because of too high variance.

A horizontal axis wind turbine has a rotor diameter of 76 m and reaches its full load output at the generator terminals of 2 MW at a wind speed of 12 m/s. The overall efficiency of the gearbox and generator is 94 %. Assume the density of air is 1.2 kg/m3 and calculate the power coefficient (Cp) of the aerodynamic rotor [6]

Question 1 [20]

A simple gear train of 30 and 50 teeth for pinion and gear wheel respectively, is used to drive an electric wheelchair at a velocity that is double the maximum velocity of slip. The pinion has an equal addendum as the gear wheel, a module of 3 mm, and a pressure angle of 14.5o. The wheelchair has a maximum velocity of 5 m/s when its pinion rotates at 800 r.p.m. Calculate:

1.1. The

1.2. The

1.3. The

1.4. The

1.5. The

1.6. The

magnitude of the velocity of slip of gears in mesh. (2) angular speed of the gear wheel in rad/s. (4) maximum length of a path of the approach in mm. (2) length of a path of a recess in mm. (7) addendum of the gears in mm. (7) contact ratio. (8)

Each filter is washed for 5 minutes every 24 hours at a wash rate of 10 mm/sec/m2 of filter area. The filter remains out of operation for a total interval of 30 minutes per day. Calculate the percentage of filter output used for washing. 

The sketch shows an object of mass 10 kg resting on a smooth plane at 25° to the horizontal. The 10 kg mass is attached to a hanging mass of 1 kg by a light cord passing over a light, frictionless pulley at the top of the plane. Determine the direction of movement when the masses are released and then use Newton’s second law to calculate the acceleration of the system and the tension in the cord.

Question 1 [20]

A simple gear train of 30 and 50 teeth for pinion and gear wheel respectively, is used to drive an electric wheelchair at a velocity that is double the maximum velocity of slip. The pinion has an equal addendum as the gear wheel, a module of 3 mm, and a pressure angle of 14.5o. The wheelchair has a maximum velocity of 5 m/s when its pinion rotates at 800 r.p.m. Calculate:

1.1. The

1.2. The

1.3. The

1.4. The

1.5. The

1.6. The

Question 2

magnitude of the velocity of slip of gears in mesh. (2) angular speed of the gear wheel in rad/s. (4) maximum length of a path of the approach in mm. (2) length of a path of a recess in mm. (7) addendum of the gears in mm. (7) contact ratio. (8)

 In a jib crane, the jib and tie rod are 5 m and 4 m long respectively. The height of crane post is 3 m and tie rod remains horizontal. Determine the forces produced in the jib and tie rod when a load of 2 kN is suspended at the crane head

 In a jib crane, the jib and tie rod are 5 m and 4 m long respectively. The height of crane post is 3 m and tie rod remains horizontal. Determine the forces produced in the jib and tie rod when a load of 2 kN is suspended at the crane head