Name: SOLUTION KEY
Quiz #6 (q6)
Machine Design
Oct. 15th, 2015
1. The part shown is 0.2 in diameter steel wire (E = 28,000 ksi), with R = 4 in, and h = 5 in. A force is
appl
PROBLEM 7.9
KNOWN: Dimensions and surface temperature of electrically heated strips. Temperature and velocity
of air in parallel flow.
FIND: (a) Rate of convection heat transfer from first, fifth and tenth strips as well as from all the strips,
(b) For ai
PROBLEM 8.3
KNOWN: Temperature and velocity of water flow in a pipe of prescribed dimensions.
FIND: Pressure drop and pump power requirement for (a) a smooth pipe, (b) a cast iron pipe with a clean
surface, and (c) smooth pipe for a range of mean velociti
PROBLEM 9.37
KNOWN: Electric heater at bottom of tank of 400mm diameter maintains surface at 70C
with engine oil at 5C.
FIND: Power required to maintain 70C surface temperature.
SCHEMATIC:
ASSUMPTIONS: (1) Oil is quiescent, (2) Quasi-steady state conditio
PROBLEM 3.85
KNOWN: Dimensions and properties of a composite wall exposed to convective or insulated
conditions.
FIND: (a) Maximum wall temperature for left face insulated and right face convectively cooled,
(b) Sketch the steady-state temperature distrib
PROBLEM 3.5
KNOWN: Thermal conductivities and thicknesses of original wall, insulation layer, and glass layer.
Interior and exterior air temperatures and convection heat transfer coefficients.
FIND: Heat flux through original and retrofitted walls.
SCHEMA
PROBLEM 1.1
KNOWN: Thermal conductivity, thickness and temperature difference across a sheet of rigid
extruded insulation.
FIND: (a) The heat flux through a 2 m 2 m sheet of the insulation, and (b) The heat rate
through the sheet.
SCHEMATIC:
A = 4 m2
k =
19—622 The L-shaped bar has mass of 8 kg/m.
in conﬁguration A, the system is on a horizontal frictionless surface or out in space‘ The two forces are
applied for a very short time. Fx: 1000 N and Fy= 1000 N.
0 Determine the CG of the system, the IG of the
R2-29.
Determine the backspin m which should be given to the y I
ZU-lb ball so that when its center is given an initial " "
horizontal velocity '00 = 20 ft/s it stops spinning and
translating at the same instant. The coefﬁcient of kinetic
friction is ,u,
[4—620
The sphere of
weight 25 lb and radius of 1
ft rolls down the hill
without slipping starting
from rest.
-Using energy, determine
the speed at the bottom of
the hill
-Using momentum,
determine the time that it takes to reach the bottom
.i 7—
9 ‘ t
I‘l-ISI‘D
O The box of the wagon has mass of loo-kg. Each of the four wheels has mass of 25-kg.
The radius of each wheel is r=.25 m. The
system starts from rest and then the force P=50N
pushes for 10 sec. Find the speed using ——> o a
each of the 3 techniq
13-C10 Each of the go’cart's front wheels
weighs 5-lb and has a moment of inertia of
0.01 slug-ftZ. The two rear wheels and rear axle
form a single rigid body weighing 40 lb and
have a moment of inertia of 0.1 slug-ft}. The
total weight of the go-cart and
17—640 The lawn roller has a mass of 80 kg and a radius of
gyration of kG=0.175 m. It is being pushed and accelerated by
the force P. The coefﬁcients of static and kinetic friction
between the grass and the roller are 115:0.12 and uk=0.10.
0 Determine the
17-621 The spool has a mass of loo-kg and radius of gyration
k0: 0.250 m. P=500 N.
A o The coefﬁcient of friction 11:035. Determine Ff, ax, a
B o The coefﬁcient of friction p=0.25. Determine Ff, ax, a
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17-C22 The assembly consists of a 3-kg sphere and a 4-kg
slender rod. The string is cut and it starts to move.
Immediately after the string is cut.
Find IO using parallel axis
Find by MO = IO
Find the mass center using techniques from Statics
Sketch the a
17-622 The spool has mass of ZS-Rg and radius of gyration of
ko=0.175 m. The force P = 100M-
@ 0 Determine the minimum p to prevent slip. Also ﬁnd Ff, a,
and a at this point.
0 If p=0.20, determine Ff, a, and a.
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17-117.
A cord C is wrapped around each of the two 10—kg disks. If
they are released from rest, determine the tension in the ﬁxed
cord D. Neglect the mass of the cord.
Also, if released from rest, use energy techniques to determine the speed of B, 038,
an
17-A20 The car has a mass of 1500-kg.
(‘1 Assume that it has enough power to spin
' the tires. The coefﬁcient of friction
between the tires and the road is u=0.7.
What is the max acceleration if the
car has front wheel drive? What are
the normal forces at
O
17-A12 The wagon and load have a mass of BOO-kg.
No friction at A or B. The wheels are small and have no
mass.
If P: 2000 N, what are the acceleration and normal
forces at A and B?
Determine the maximum force P that can be applied 0'5 m
such that all of
' 17—102.
\7 1
The 2—kg slender bar is supported by cord BC and then
I released from rest at A. Determine the initial angular
acceleration of the bar and the tension in the cord.
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14-xx This is a 5 point homework problem. /, m
This illustration shows an airplane doing a loop at a \
fairly low speed. My son is a pilot in the Air Force and \
does these loops at 500 mph in a jet. For this problem p "\
use the English system of units i
‘1 323 ML“?
. 5.7,
w 16-014 At the instant shown, determine
vain“, and (use using all three methods:
rel
tive equation, IC method, and absolute.
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gran/.5513. 53.; (5525044.ng
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10 ft/s
O 15-A30 The cart weighs SO-Ib. The rollers
are frictionless. The suitcase weighs 30-lb
and is thrown horizontally onto the car at 10
ft/s. The coefﬁcient of friction u=0.4.
- Using conv of momentum: Determine
the ﬁnal speed of the system.
- Using
J‘s—k2!)
m From 15-34 in your book, plot the value of velocity vs time from t=0 to t=10. What is the value
of v at 5? What is the minimum velocity and at what time does it occur?
Use a graphing program such as this one for the iPhone/iPad. This one has ni
15-75.
. The 1-kg ball is dropped from rest at point A. 2 m above the
smooth plane. If the coefficient of restitution between the
ball and the plane is e = 0.6. determine the distance d
where the ball again strikes the plane.
Putt/c3 -—? l/ZP = V”
*15—44.
a Two men A and B, each having a weight of 160 lb, stand on
the ZOO-lb cart. Each runs with a speed of 3 [1/5 measured
relative to the cart. Determine the ﬁnal speed of the cart if
(a) A runs and jumps off, then B runs and jumps off the
same end,
11+ - C [D
14-gg The double pulley consists of two parts that are attached to
one another. The pulley has negligible mass.
The system is released from rest. Using energy methods, determine the
speed of A after it has traveled 1 foot.
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If 9 = 0.5t and f: 0.5 + 0.56, find r, f, 'r', B, 9, 9,
evaluated at t=2 sec.
If the mass B is .Zkg, draw the F80 and find the
magnitudes of all of the forces involved at t=2
sec. What is the coefficient of friction?
t = 2566 (a)
a. 3 , [D- t