Engineering Answers

(a)  Air at 2.01 bar, 27° C, initially occupying a volume of 0.015 m³, is compressed reversibly and adiabatically by a piston to a pressure of 6.8 bar. Calculate:

(i)                The final temperature                                                                       (6 marks)

(ii)             The final volume                                                                              (4 marks)

(iii)           The work done on the mass of air                                                (5 marks)

A DC shunt motor is driving a constant torque load at the rated speed and rated terminal voltage. The motor has a terminal voltage of 115 V with speed of 312 rpm and the field constant is 3 V.sec. If the terminal voltage of the motor is reduced by 10 %, calculate the motor speed and assuming that the field voltage is also reduced by the same ratio.

a four-cylinder petrol engine has a swept volume of 2000 cm³ and a clearance volume in each cylinder is 60 cm³.Calculate the air standard cycle efficiency

QI: NGO ii - CLO 2 - PI-24 In an epicyclic gear train, an arm carries two gears 1 and 2 having 40 and 50 teeth respectively. The arm rotates at 160 rpm cew about the center of gear 1, which is fixed. 1) Predict the speed of the gear 2. 2) Analyze the performance of this mechanism if the arm speed reduced to 110 rpm.

A 6600 V, y-connected, 3-phase alternator has a synchronous reactance of

6 Ω

per phase and a negligible resistance. At a certain field current the armature is

known to induce 5800 V per phase. Calculate the maximum power that can be

developed by the alternator at this excitation.

 A cone of base diameter 40 mm and height 50 mm is resting centrally on the top of square frustum whose smaller base is 40 mm, larger base is 50 mm and height 60 mm. The square base frustum is resting on its smaller base. Draw an isometric view of the solids.

The electromagnetic spectrum contains various types of radiation with dierent properties. The James Webb Space Telescope is not like an optical telescope at home and does not capture visible light; instead, it observes the sky in the infrared spectrum. Explain what infrared radiation is and answer the following questions: How is infrared radiation dierent from visible light? Why does the JWST observe infrared light, and what are the scientific advantages for astronomers

The James Webb Space Telescope is positioned around 1.5 million kilometres from the Earth on the side facing away from the Sun. The telescope remains at this distance and orbits around the Sun with the Earth’s orbital velocity. (a) Why is it important to position the JWST behind the Earth? (b) Determine the angular velocity ω of the telescope as it orbits around the Sun. The centrifugalFω and gravitational forceFG are acting on objects orbiting the Sun: F = Fω−FG (c) Based on this, how much should the telescope accelerate towards or away from the Sun? (d) Why is the orbit of the telescope stable nonetheless? What otherforces need to be considered

Assume that a gravitational anomaly in the solar system has shied afield of asteroids into Earth’s orbit, and the field is now moving directly towards Earth. The asteroid field has a density of ρ (asteroids/volume), and each asteroid has an average mass of m. The asteroid field stretches over a distance d in Earth’s path. Assume that the Earth moves with a velocity of v, the asteroids with u, and that v  u. Let R be the radius and M the mass of the Earth. The Earth collides with the asteroid field: v u Show that the slow-down ∆v of the Earth due to the asteroid collisions is given by: ∆v = v  1 − 1 1 + πR2dρ m M 

The James Webb Space Telescope (JWSP) was finally launched into space on December 25, 2021, and is about to become one of the most important scientific instruments of our time. Name the major components of the JWSP shown in the figure below: (A) (B) (C) (D) (E) (F) (G) (H) (I) (J)