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
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:
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
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:
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: 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))
=
=
=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
= 894.61g
m = 2.54mol / 0.89461Kg
m = 2.84 m
Ans
Pf =
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
o
F, what is the extra work done at 100 oF.
Solution:
P = (80 psia)(1ft / 12in)2 = 11520 lb/ft2
=
= 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
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)
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%
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 =
δp =
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)
X=
To God Be the Glory
= 0.24
Page 2
GEAS – November 2010
Q: A shaft has a diameter of 10cm(100mm) and wall
thickness of 0.4cm(4mm) and it is subjected to a torsional
moment of 10kN-m(10x10^6 kN-mm). Calculate the
percentage error of the maximum shear stress.
A: 3.3%
Calculating the maximum shear stress,
Q:
a.) Estimate the rate of heat loss of the 3m x 10m
wall composed of 2.5cm pine wood, 8cm of wool
insulation, and 1.5 cm of plaster. The temperature
of the room is 22°C and the outside air is -20°C.
J=
=
= 3.53x106
The conductivity in
of pine = 0.15,
wool insulation = 0.038, plaster = 0.81 and the
σMAX =
=
= 152
Calculating the average shear stress;
convective coefficient
of air = 12.
b.) Calculate the given heat coefficient of the 3m x
10m wall.
σAVE =
=
= 147
Calculating the percentage error;
A:
% error =
For a:
x 100% = 3.3%
Q: A microwave oven has a diameter of 2cm and a length
of 2m. The oven is maintained at 1000°C while the wall is
at 500°C and has an emissivity of 0.85. Calculate the ………
A:
Formula to use is
______= σƐA(T14 – T24)F1-2
-11
)(0.85)(0.25)(12734-5734) = 30
= (5.67x10
Where,
σ = Stefan – Boltzmann constant
= 5.67x10 -11 (sa coaching notes)
T = should be in Kelvin
A = area = 2Πrh =2Π(0.02)(2) = 0.25
Ɛ = emissivity = 0.85
F1-2 = 1 since the oven is an enclosed element
***guyz xenxa wla ko kbalo sa gi-ask ug unit sa final
answer…kamo n bhala mgsabot mga bright btaw tng
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Q: What is the activation energy in (kJ/kg mol) of the
system if the eQuilibrium constant is increased 10 times
when the temperature of the system is doubled?
A:
For b:
Q: A potential difference of 87.0 keV is applied between
the filament and target in the x-ray tube used in local
clinic to look for broken bones. What is the shortest
wavelength x-ray produced by this tube?
A: 14.3 pm
Solution:
Note:
To God Be the Glory
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GEAS – November 2010
Q: The position of a certain object is given by:
. How long will it take for the velocity
to be zero?
A: t=3s
Q: In calculating the modulus elasticity of a shaft, you
used a uniform diameter of 25 mm. However, you later
realize that the shaft actually tapers from 26 mm to one
side and 24 mm to the other side. What is the error
committed in calculating the modulus of elasticity of the
shaft?
A: 99.84%
Q: Two metal shafts are compared: one is solid and has a
diameter of 100cm, the other is hollow with inner
diameter 50cm and outer diameter 100cm. What is the
relationship of the *(torsional stress) present in between
shafts?
Solution:
Note: a hollow shaft always has a *(torsional stress) 6.67
times that of a solid shaft with eQual outer diameter
regardless of the inner diameter.
In solving for k:
*not sure
A: 6.67 times
Substitute:
Q: A trough is used for animals’ drink has dimensions:
2.1m long, 7.13cm wide and 30cm deep. It contains
10.62kg of a fluid with
. How deep is the fluid?
Q: A wave passes from Medium A to Medium B. If the
angle of incidence is 40o and the angle of refraction is 30o,
what medium does light travels the fastest?
A. Light travels faster in Medium A than in Medium B.
Solution:
Snell’s Law:
A: h=16.6cm
Q: A steel wire (coefficient of thermal expansion of 11.7 x
10-6) of has a diameter of 5 cm and a length 80 cm. What
compressive stress induced in this wire that restrained
from moving if it is increased by 100° C.
Since
Medium B.
, light travels faster in Medium A than in
Answer: 234MPa
Solution:
Q: A beam has a width of 60cm, and a depth of 20cm. it is
designed to carry a bending moment of 6000Nm, how
much is the flexural stress developed in the beam?
A:
To God Be the Glory
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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:
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.
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:
A:
Solution:
formulae:
where:
Since change of enthalpy is eQual to heat removed or
attracted,
T=460 + F
Problem: What is the solid shaft’s twisting moment if it is
driven by a turbine 70hp, turning 200rpm?
Answer:
P = 2πfT
(70hp)(6600 lb-in/s) = 2π(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?
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:
m
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
To God Be the Glory
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GEAS – November 2010
m=
wrt the object.
; negative sign indicates reduction in size
m=
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:
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
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.
Solution:
Formula:
A.
Solution:
=
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:
To God Be the Glory
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GEAS – November 2010
To God Be the Glory
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