GEAS problems, general science, Exercises of Science education

Download GEAS problems, general science and more Exercises Science education in PDF only on Docsity! GEAS – November 2010 Q: A spherical tank is made from 2.5mm thick plate and is subjected to an internal pressure of 1400kPa. If you are told that the tank cannot be subjected to a stress more than 100MPa, what diameter of the tank would you use? A: 714 mm Solution: D = = D = 714 mm Q: A truck container is filled with 37,000 liters of diesel fuel @ the origin. The driver experienced a cold weather @ the destination 23 kelvin lower than the origin. The coefficient of volumetric expansion of a diesel fuel is 9.5x10-4 /⁰C. How many liters of diesel fuel were delivered @ the destination? A: 36,191.55 L Solution: ∆V = αvVo∆T = (9.5x10-4)(37000)(-23) ∆V = -808.45 L Vt = Vo + ∆V = 37,000 – 808.45 Vt = 36,191.55 L Q: A truck moves from rest and accelerates at a constant rate of 10 m/s2, passes through a circular curve with radius of 1000 m. How long does the truck move before the normal component of acceleration eQuals the tangential acceleration? Solution: Q: In eQuilibrium, Mars emits the same radiation as it absorbs. If the orbital radius of Mars is 1.5 times the radius of the earth around the sun, determine the relationship of temperature of Mars to earth. Thus, the temperature of Mars is ________ times that of the earth. Solution: Q: Find the minimum power reQuired when the pressure changes from 2kPa to 6 MPa for a mass flux of water 10 kg/s. Solution: Q: The heart pumps blood into the aorta, which has an inner radius of 1.0cm. The aorta feeds 32 major arteries. If the blood in the aorta travels at the speed of 28 cm/s, what is the average speed of the blood in the arteries? Assume the blood can be treated as an ideal fluid and the arteries each have an inner radius of 0.21cm. Solution: Q: Ten cubic ft of air is cooled at a constant pressure of 80psia. What is the change in internal energy if the initial temperature was 180OF? [ Solution: To God Be the Glory Page 1 GEAS – November 2010 Q: The density of 2.54 M aQuaeous solution of methanol (CH3OH) 0.976 g/ml. What is the molality of solution? If methanol is 32.04 g/mol Solution: (1L soln)(1000mL soln / 1L soln)(0.976g / 1mL soln) = 976g Mass of H2O = (976g- (2.54mol x 32.04g/mol)) = 894.61g m = 2.54mol / 0.89461Kg m = 2.84 m Ans Q: A ten cubic feet of air is to be cooled down with a constant pressure of 80 psia. If the initial temp is at 180 oF, what is the extra work done at 100 oF. Solution: P = (80 psia)(1ft / 12in)2 = 11520 lb/ft2 T1 = 180 + 460 = 640 R T2 = 100 + 460 = 560 R V = 10 ft3 R = 53.53 lbft/mol R PV = nRT (11520)(10) = n(53.53)(640) n = 3.36 mol W = m (T2 – T1) W = (3.36)(560 – 640) W = - 269.01 Ans Q: Two bars, prismatic bar and conic bar, are vertically hanged by their own weight. If the length, density and modulus of elasticity is the same. Determine the ratio of their elongation. Soln: δc = c = δc = p = = = = 3 Q: In a cylinder, an oxygen gas has 12 liters at 20 oC with a pressure of 15 atm. If the temperature in cylinder is increase by 35 oC and the volume is reduced to 8.5 liters. Determine the pressure. Assume the gas us ideal Soln: PiVi = nRTi PfVf = nRTf Pf = = = 22.26 atm Q: A truck starting from rest accelerates at a rate 10m/s2 around a circular curve of radius 1000m. How long before the normal acceleration component eQuals the tangential acceleration? A: 500 m Q: An electronic engineer invented an engine uses a 1600°C geothermal heat. It exhaust to the 20°C environment, what is the maximum efficiency of the engine? A: 32.33% Q: Calculate the normality of 0.25 mL of NaOH if it needs 0.2 mole and 0.3mL of HCl. A: 0.24 In neutralization, the normality of base is eQual to acid 0.2 (0.3mL) = x (0.25mL) To God Be the Glory Page 2 GEAS – November 2010 Problem: A cantilever beam of length 1m carries a uniform load of 200 N/m. What is the maximum moment of the beam? Solution: Problem: What is the change in enthalpy if 10 cubic feet of air are cooled at constant pressure of 80 psia? The initial temperature was 180 degree Fahrenheit and final temperature is 100 degree Fahrenheit. Solution: Since change of enthalpy is eQual to heat removed or attracted, Problem: What is the solid shaft’s twisting moment if it is driven by a turbine 70hp, turning 200rpm? Answer: P = 2πfTfT (70hp)(6600 lb-in/s) = 2πfT(200rev/min)(1min/60s)T T = 22070 lb-in Problem: Let a 1kg liQuid be converted to steam by boiling at 1atm (101.325kPa). How much work is done in converting the liQuid with initial volume of 1x10^-3 m^3 to 1.671m^3 of steam? Answer: W = P(Vfinal-Vinitial) W = (101.325)(1.671-1x10^-3) W = 169kJ Problem: A vessel and piston is used to compress 1 pound mol of ideal gas. If the ideal gas is compressed at a constant temperature of 100 degrees Fahrenheit from 20 atm to 5 atm, what is the work done? Problem: A block has dimensions of 20cm (width) x 60cm (height) x 80cm (length). The 20cmx80cm plane is secured to a horizontal slab. If the block is subjected to a shearing force of 1000kN, what is the shearing strain of experienced by the block? The modulus of rigidity of the block is 83x106 kPa. Q: A 1-lb gas is being compressed; calculate the change in entropy in Btu/R, if the parameters are changing are from 14 psia at 60 degrees F to 84 psia at 460 degrees F. A: Solution: formulae: where: T=460 + F n=1.4672 Q: A beautiful Otot-Otot flower of 1.2 cm in diameter is being gaze at a distance of 90 cm on a camera whose focal length is 150 mm. Calculate the image size formed by the flower. A: 0.24 cm Solution: formulae: To God Be the Glory Page 5 GEAS – November 2010 m m= ; negative sign indicates reduction in size wrt the object. m= 0.24 cm Q: For intrinsic silicon, the room temperature electrical conductivity is 4x10-4 (Ω-m)-1. The mobility of hole and electron are 0.14 and 0.048 m2/V-m. Calculate the concentration of hole and electron. A: 1.33x1016 m2/V-m Solution: Formula: = Ans: P = 1.33x1016 m2/V-m Q: Calculate the change in enthalphy of helium if it is heated reversibly at constant pressure of 18psia, 80 deg F to 200 deg F in a steady flow. A: 0.25 Solution: ; where Ans: Q. A heat engine has a capacity 0f 3140 watts and an input rating of 735 watts. What is the coefficient of performance of the engine? A. 4.27 Solution: Q. Given a parallel wire line and that 5 electrons flow to the right of one of the wires that took 0.04s. Find the current in the parallel wire line. A. Solution: To God Be the Glory Page 6 GEAS – November 2010 To God Be the Glory Page 7