PHYSICS 143 PASS QUESTIONS

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UNIVERSITY OF GHANA &middot;
DEPARTMENT OF PHYSICS &middot;-
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FIRST SEMESTER EXAMINATIONS: 2014/2015 ‘
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PHYS 143: MECHANICS AND THERMAL PHYSICS (3 Credits)
—ATTEMPT ALL QUESTIONS
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TIME ALLOVVED: TWO AND HALF HOURS
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Instructions
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PRINT your student ID number in the space provided at the top of each page.
Each question or partial statement is followed by five suggested answers or completions.
SelectI
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Example
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The SI unit ofmass is
N.
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Values of Physical Constants
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Acceleration due to gravity
g = 9.81 m
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* 1 Molar mass ofHydrogen gas
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= 2 kg / kmol
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Molar mass of Oxygen gas
= 32 kg / kmol
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of the Earth
RE = 6.37&gt;&lt; 106
mI
Mass ofthe Earth
ME = 5.98 &gt;&lt; 1024
kg*
kg‘2
Universal gravitational constant,
G = 6.67 &gt;&lt; 10*1 N m2
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R = 8.3149 J mol&quot; K4
NA= 6.02&gt;&lt;1022 mol&quot;
1kB = 1.38&gt;&lt;10&deg;23 J K&quot;
Universal gas constant,
number
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Bo1tzman11’s Constant
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EXAMINERS: DR. E. M. BAIDOE-ADEITEYE, DR. S. ATARAH, DR. H. A. KOFFI &amp; MR. A. AMANKWAH
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PHYS 143: MECHANICS AND THERMAL PHYSICS
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ExAM1r~1ERs;&curren;1&gt;„.E. M. &szlig;A1&curren;oE-A-DELEYE, DR. s. ATARAH, DR.
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CANDIDATE ID NUMBER:
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The work done by a conservative force between two points is.
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Never completely recoverable.
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2. A woman runs up a flight of stairs. The gain in her gravitational potential energy is U. If she
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up the samefstairs at twice the speed, what is her gain in potential energy?
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3. A swinging simple pendulum is acted upon by the&szlig;following forces:
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force of gravity.
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II. air resistance.
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Which of these forces does no work on the pendulum? &middot;*
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The work — energy theorem is valid for all objects or systems. _}
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E. kinetic is doubled.
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PHYS 143: M.ECHANtCS' AND THERMAL BHYSICS i
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EXAMINERS: DR. E. M.
BAIDOE-ADELEYE, DR. S. ATARAH, ADR. H. AI KQFFI &amp; MR. A. AMANKWAH
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D. 1, II and
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AE. Ionly III
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A. kinetic energyis
conserved.t
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B. kinetic energy is gained.
C. kinetic energy is lost.
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4. Which ofthe following is not true?
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6. Which ofthe following is correct?
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A. &deg;Whether a collision is elastic or not,
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B. Impulse is a vector that takes same
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direction as the initial velocity of the moving body.
momentum.
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a particle is
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8. The magnitude of the displacement of
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particle
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the surface of the earth . .
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9. Which of the followingstatements is
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resistance?
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A; The horizontal velocity is constant.
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a projectile is doubled, its range &quot;
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EXAMINERS: DR. E.M.BA1Deu1a-AADELEYE,. DR. s. ATARAH, DR. HAA. kom&amp;MR.
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Page 4 of 11
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I2. 4Two objects with different masses collide and stick to each other. Compared to
before the collision,
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collision
has
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A. the same total momentum and the same total kinetic energy.
B. the same total momentum but less total kinetic energy„_
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C. less total momentum but the same total kinetic energy.
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D. less total momentum and less total kinetic energy.
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E. more total momentum and less total kinetic energy.
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13. A box is pushed across a horizontal flat surface with an initial Velocity of
v. It comes to rest after
a displacement d. Assuming that all the kinetic energy of the block is
eventually dissipated by
_ friction, determine the coefficient
of kinetic friction uk if the acceleration due to gravity is g.
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14. A ball of mass 0.40 kg is initially moving the left at 30 ’m/s towards
a wall. After hitting the wall,
_ 1 . the ballmoves to the right at 20 m s&quot;. What
is the impulse of thenet force on the ball during its
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collision with the wall?
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B. 20 kg m s&quot; to the left
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-4.0 kg m s&quot; to the right
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D. 4.0 kg m s&quot; to the left .
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E. 40 kg m s&quot; to the left
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15. A constant horizontal force of 20 N is applied tp a 3 kg block
that is initially _at rest on a horizontal
table as shown in Figure 1. The kinetic friction between the
block and table is 10 N. Find the
speedI
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of the block after it has been pushed 3 m.
.-.
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i6.30ms*1—
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D. 3.17 m s‘1
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PHYS 143; M1ac11A1~11cs AND THERMALI-Pl-IYSICS
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DR. s. ATARAH, mz. 1-1. A. KOFFI &amp; MR. A. AMA1~11&lt;wA1-1
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Page 5 of 11
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the potential energy
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A spring with force constant k =;300
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5.0 m s&quot;, releases a
with a constant velocity of magnitude
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balloonist,_rising
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17. A
ground. AfterAit is released, the sandbag
1 . &Auml; &Auml; sandbag at an instant when the balloon is 40 m above the
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height of the sandbag from the ground.A’.
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is in free fall. Determine the maximum
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force. The2 pull is at
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horizontal and frictionless floor by a 90.0 N
18. A 60.0 kg bag is pulled on a flat
the bag whilst
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the normal force exerted by the floor on
an angle of 30.0&deg; to the floor. Detennine ‘
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the pulling forceA acts.1 A
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19. What is the work done by the force if
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c. 402.5 N
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2.
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the speed ofthe object after it has fallen 75
is released‘ from rest. Calculate
2
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20. AA.
A 75 g object
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m&Auml;s&middot;‘
2
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1.7 m&middot;s‘1
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PHYS 143: MECHANICS AND THERMAL PHYSICS
H. A. IQOFFI &amp; MR. A. AMANKWAH
ATARAH,
DR.
S.
DR.
E.-MLBAIDOE-AQELEYE,
DR.
EXAMINERS:
Page6of11
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A 21. A 50 g. object connected to a spring with force eonstant&middot;k = 1.2 N
is pulled horizonfally to
the left on a frictionless surface. If the spring is stretched 10 cm and released from rest,
calculate
the speed. when the object has travelled 4 cm toward the equilibrium position.
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B. 0.20 m s&middot;‘
A. 0.11mS&middot;‘
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D. 0.87 m s&middot;‘
E. 1.50 m
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10 m
B.C. 7.5.00 mm I
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A. 3.5 m
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B. 27.8 m 1
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A.B. 11..96X104J
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24. A 1500 kg car is moving with a speed of 25.0 m s&quot;. How much energy
is required to stop the car?
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.
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E. 9.4 X 105.1
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is 2.0 rad s&quot;', find the angle the wheel rotates through in 2.0 s.
.
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I25.
A wheel is rotating with a constant angular acceleration of 3.50 rad s&deg;2. Ifthe
initial angular
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23. A stone is thrown horizontally with an initial speed of 8.0 m s&quot; from the edge
of a cliff The time—,
it takes to fall from the top of the cliff to the bottom is 3.4 s. Calculate the
height of the cliff.
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A
D. 8.0 m
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1
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object moves 4.0 m north and then 3.0 m east. Find the magnitude of the displacement.
“
Velocity
’
1
1
A
I
.26. A 0.30 kg mass, attached to the end of a 0.75 m string,
is whirled around in a horiaontal plane. 1f
A
_
the maximum tension that the string can withstand without
breaking is 250.0 N, determine the
&middot;
A. 22.40 m s&deg;‘
maximum tangential speed.
_
B. 25.00 m s&quot;
A
‘
1
‘
_IAA
c. 19.40 m S4
.
1
D. 32.70 m s&quot;
&middot;
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A E. 275.00 m s&middot;‘
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&middot;
\‘wg
.
A
7
A .4
PHYS 143: MECHANICS AND THBRMAL PHYSICS
A
EXAMINERS:
DR. E. M. BAIDOE-ADELEYE, DR. SQATARAI-1; DR. H. A. KOFFI &amp; MR. A.‘
A
AMANKWAH
3
.
Page70f111.
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CANDIDATE ID NUMBER: |__\__|?_|__|_|__|__|__| V
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s'! while covering 75 m. Find the time
27. A car’s velocity increases uniformly from 5.0 m s&quot;1toV20 m
VVA.
.
. I
taken to cover the distance.
.‘
_
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10 s
’
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B!60s
V
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.resultant fofce. i ' i '
{W
20.0} N. Calculate the magnitude of the V
A force-(15.01 Iyj 10.0}) N is added to another force
-,,428.
&middot;
A&Uuml;&Uuml;.0 N
3
V
i
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3
&deg;.
{
3”
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&middot;
.
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&deg;E.
Ic.
26.1 N
&Uuml;
3
-1
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D. 32.3N
V
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&middot;
4x3 where x is inmetres, aets on a particle
29. A position-dependent force in Newton, F (x) = 3xZI +
..
= 4 m. Calculate the work
i iidone byithe‘ __
&middot;
which moves on the x-axis from the origin to the point x
Vi
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33.8N
force. ~1
3
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&middot;
1
.-
-.
{Q
r
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theVangu1ar.
torque of 40 N m. Determine
30. An engine develops a power of 16001r W at &Auml;istant n
Q 3
‘
‘
_3 3 &deg;
3 ‘
.V
&middot;
3
V
i{
- velocity of the engine in revolutions per minute.
”
_
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.
A. 1025 rev min']
.
V
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B.
V
1780 rev min&quot;
,
V_
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D. 1320 rev min&quot;
.
E. 1360 rev min']
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DR.
M.
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EXAMINERS: DR.
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3
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31. Which of the following statements is true?
An example of athermometric
&quot;‘ property is
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II. pressure of a confined gas
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AA.
I and II only
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I and IH only
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A
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C. II and III only
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D. I,_II, and III
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32. Which of the following is not correct?
B/[
F&quot;I.
Real gases obey Boyle’s law at high temperatures and low pressures. X
.
,I
F
II. Ideal gases obey Boyle’s law only at high pressures and&middot;low temperaturesf
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B. I and IH only
C. II and III only
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In an
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isobaric expansion of a gas,
\1
work done by the gas is independent of its pressure.
A
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5
II work done by the gas is proportional to the change in its volume. / ‘
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III work is done by the gas at the expense of its intemal energy. A F
A
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E. I and III only A
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34. The first law of thermodynamics is most closely related to 5A
_
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Q
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A. the definition of the. absolute zero.
A
A-B.
the definition of an ideal gas.
-_
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C. theconservation of energy.
‘
_
5 .
D. thermal expansion.
_
F
E. the conservation of momentum.
l
A
Q
F
Q
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is added to the gas in one cycle?
A. 2W
B. W
C. % W
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p F &middot; 35. Anideal gas undergoes a cyclic process in which total work Wis done by the gas. What total heat
Q
.
&auml;&auml;i
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A R1-ws 143. M6cHAN1cs AND THERMAL Ruvsics
EXAMINERS:&middot;DR. E. M. BAIDOE-ADELEYE, DR. s. ATARA1-1, DRA.&middot;1-1. A. korri &amp; MR;FA. AMANRWA1-1
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9
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444
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A. 116 J
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4V
4
13. 320 J
4
C. 575 J
4
4
4
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D. 640 J
4V 9:13. 0J
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A. as Q.
4
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at 620 K takes _in 550 J of‘beatVat this
reservoir
high-temperature
whose
engine
Carnot
39.A
thetbemial
the low&middot;temperature reservoir. What is
i
temperature in each cycle and gives up 335 J to
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efficiency of the cycle?
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125K
D. 275K 4
4
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final temperature of the gas.
twice its original volume. Calculate the
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&middot;{ @226K
&middot; . 298 K
V
V *
44 4
9.
E. is zero.
4
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V
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from an initial volume of 2
38. A quantity of air expands adiabatically
4
V
9
4
4
&middot;i
&deg; .
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work done by the engine
from a hot reservoir.4 The amount of
9
must be greater than Q.
” B.
C. must be less than Q.
D. could be greater than Q. 4
j
9
4
4
37. A heat engine absorbs heat
.
9
m3 undergoes a quasi&Auml;
250 kPa and a volume of 4.5
of
apressure
&deg;C,
100
at
initially
An ideal gas
'36.
change in the internal
pressure is reduced to 150 kP4a. Find the
static, 4isothermal expansion until its
V
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4
.
.
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an ideal gas at a temperature of 0 &deg;C and a
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40. Calculate the volume of two moles of
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V
99 9 ‘A.1.1&gt;&lt;10&middot;2m3 V
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.
m3
9V
9
.4
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&middot;
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9
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4.5 210-2 m3 -
. 7.7 &gt;&lt;10&middot;2m3
4
4. PHXS 143: MECHANICS AND THERMAI. PHYSICS
_
.4
.
4
*4
..
_
{
DR. H. A.4KOF4FI &amp; MR. A._AMANKWAl-1
EXAMINERS: DR. E. M. BAIDOE-ADELEYE, DR. S. ATARAH,
Page
4
4
.
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CANDIDATE ID NUMBER: |_|_|_|_|_|_|_|_|
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41. Thetemperature of an ideal gas initially at 47 &deg;C changes
such that its pressure is doubled and its
volume reduces to two-thirds of its origina11value. Calculate_the
new temperature of the gas.
1
1
|
&middot;
I
A. 153.67 &deg;C
B. 217.76 &deg;C
c. 374.76 ec
OC
5
1
1
1
&middot;
B. 591.67 CTC
D. 462.67
1
1
1
.
42. An ideal gas sample has a pressure of 2.5 atm and a
volume of 1.0 m3 at a temperature of 30 &deg;C.
Determine the number of moles of gas in the sample.
1
1
1
1 A. 9.9 X_10“‘ 1
I
1
&middot; 1 &middot; A. 1.05_&gt;&eacute;l05J 1
B.
‘
1 c. 11.0X1_0&middot;2&raquo;
10.1 ‘15
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&middot; 1 1
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11
&middot;
1
_ 1
B. 250
1
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5
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11
V1
1 &middot; 43. How much heat is required to change 0.50 kg of ice 1at 01 &deg;C to water
at 50 &deg;C?
1
1
D. 4.38 X 1051
1B. 1.13X11051
l1
1
.
15 15
1
1
1 1
1
5
1 .
_
1
15
1
1
B. 1.67 X 105 1 1
1
1c.
_
1
2.71 X _105
I
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1
.
7 1 15
f
1
1
,
1
44. To raise the temperature of a 2.00 kg piece ofmetal from
20 &deg;C to 100 &deg;C, 61.8 kJ ofheat is added. 1
.1What is the specific heat of theq?11/etal? 1
K‘1‘
1
1 &middot;
.
&middot;11
V
I
A. 0.390 kJ kg'
1B. 0.310 kJ kg&quot; K1'
I
1 c. 1.65k1kg&middot;1.K&middot;‘
1 ‘ D. 1.24 kJ kg&quot; K1'
1&lt;&middot;‘
B. 0.770 kJ kg'
I
1
1
1 &middot; 1
1 1
1
1
. 1
.
1
1
545.
A refrigerator extracts 25.0 kJ from a cold reservoir
and rejects
the coefficient of performance of this refrigerator?
I
5
,.1 &auml;5
1 1 11
5J
1
1
A. 2.5
5
35.0 kJ to a hot reservoir. What is
11
5
1 1
1&eacute;
1
1
1f
5 B. 3.5
1
.
1
1I
-1
C. 1.4
1
.D.
5.0I
1
E. 4.0
5
5
1.
1
1
/
II
1
.1
&middot;
’
5
PHYS 143: MECHANICS AND THERMALPHYSICS
5
EXAMINERS: DR. E. M. BAIDOE-ADELEYE, DR. S.
ATARAH, DR. H. A. KOF1&sect;l &amp; MR. AI AMANKWAH
1
1
Page 11 of11
11 „
1
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1
1
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