Mechanical Engineering Answers

A vertical diesel engine running at 350 rpm develops 600 kW and has 4 impulses per

revolution. If the fluctuation of energy is 25 per cent of the work done during each

impulse, estimate the cross-sectional area of the rim of the flywheel required to keep the

speed within 2 rpm of the mean speed when the mean peripheral speed of the rim is 1350

m/min. Cast iron has a density of 7.2 Mg/m3

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1) A 400 V, 50 Hz 6 pole star connected three-phase induction motor consumes 75 kW with a line current of 75 A and runs at a slip of 2,5 %. If the stator iron loss is 2 kW, the windage and friction losses is 1,2 kW and the resistance between two stator terminals is 0,32 ohm, calculate:

a)    the power supplied to the rotor (Ps),

b)   the rotor copper loss (PcuR),

c)    the power supplied to the load (Pout )

d) the efficiency and

e) the shaft torque developed.

A delta connected motor has a resistance of 850 mohm and inductance of 2,5 mH. This motor receives a line voltage of 400 V at a frequency of 50 Hz. This supply is obtained from a 50 kVA delta/star transformer. This transformer has a no load current of 2,55 A at a lagging power factor of 0,121. Fully describe the primary line current of this transformer for the given load, when it is fed by 11 kV transmission lines.

Knowing that at the instant rod BD rotates with a constant counterclockwise angular velocity @, = 2 rad/s,

determine (a) the angular velocity of rod AD and the relative velocity of collar D with respect to rod AD, (b) the

angular acceleration of rod AD and the relative acceleration of collar D with respect to rod AD.

Two liquid streams are pouring in a container, 8 in. diameter and 15in. high. The mass flow rate of stream A is 1.2 lb/sec and the volume flow rate of B is 0.035 ft3/s. If the specific gravities of A and B are 1.1 and 0.9, respectively, What is the gage and absolute pressure at the bottom of the filled tank in psia.

Draw the profile of a cam in which the follower moves with simple harmonic motion during ascent while it moves with uniform velocity motion during descent. The other data is as follows.

Least radius of cam = 50mm; Angle of ascent = 480; Angle of dwell between ascent and descent = 420; Angle of descent = 600; Lift of follower = 40mm; Diameter of roller = 30mm; If the cam rotates at 360 r.p.m. anticlockwise, find the maximum velocity and acceleration of the follower during descent.

A Fahrenheit and a centigrade thermometer are both immersed in a fluid. The Fahrenheit numerical reading is twice that of the centigrade reading. What is the temperature of the fluid in Rankine and Kelvin scale?

An inhabitant of another planet weighs 50 lb on a spring type of scale in the planet atmosphere, where the local gravity

acceleration is g = 6.0 fps2. This inhabitant appears in St. Michael, Alaska, where the local gravity acceleration is g=32.22 fps2. For this outer-space being, determine (a) his mass in lb in slugs on his native planet, (b) his mass in lb and slugs on earth (c) his weight as indicated by a spring type scale on earth.

A hiker is carrying a barometer that measures 29.92inHg absolute at the base of the mountain. The barometer reads

25.5inHg absolute at the top of the mountain. The average air density is 0.076 lbm/ft3, the gravitational acceleration remains constant at 32.174 ft /s2. What is the mountain’s height?

At 24° latitude, the gravitational acceleration as a function of elevation z above sea level is given by g=a-bz,

where a=9.807 m/s2 and b=3.32x10-6 s-2. Determine the height above sea where the weight of an object will decrease by 1 percent.