Answer:
[tex]\mathbf{t_f = 1436.96 \ sec }[/tex]
Explanation:
Given that :
The strength and stability of tires may be enhanced by heating both sides of the rubber ( 0.14 W/m·K, 6.35 × 10^-8m^2/s)
i.e
k = 0.14 W/mK
∝ = 6.35 × 10⁻⁸ m²/s
L = 0.01 m
[tex]B_1 = \dfrac{hL}{k} \\ \\ B_1 = \dfrac{200*0.01}{0.14} \\ \\ B_1 = 14.2857[/tex]
We cannot use the model of Lumped Capacitance; SO Let assume that Fourier Number [tex]F_o > 0.2[/tex]
⇒ [tex]\dfrac{T_o - T_ \infty }{T_i - T_ \infty} = C_1 exp (- \zeta_i^2 *F_o)[/tex]
From Table 5.1 ; at [tex]B_1[/tex] = 14.2857
[tex]C_1 = 1.265 \\ \\ \zeta_1 = 1.458 \ rad[/tex]
[tex]\dfrac{170-200}{35-200} = 1.265 exp [ - (1.458)^2* \dfrac{ \alpha t_f}{L^2}][/tex]
[tex]In ( \dfrac{0.1818}{1.265}) = \dfrac{-1.458^2*6.35*10^{-8}*t_f}{0.01^2}[/tex]
[tex]-1.9399=-0.001350 *t_f[/tex]
[tex]t_f = \dfrac{-1.9399}{-0.001350}[/tex]
[tex]\mathbf{t_f = 1436.96 \ sec }[/tex]
If gear X turns clockwise at constant speed of 20 rpm. How does gear y turns?
Answer:
Gear Y would turn Counter-Clockwise do to the opposite force created from gear X.
Hope this helped! Have a great day!
A particle is emitted from a smoke stack with diameter of 0.05 mm. In order to determine how far downstream it travels it is important to find its terminal downward velocity. If it has a density of 1200 kg/m3, its terminal downward velocity (cm) is: (assume the drag coefficient is 24/Re and the volume of a sphere is 4/3 pi R3)
Answer: downward velocity = 6.9×10^-4 cm/s
Explanation: Given that the
Diameter of the smoke = 0.05 mm = 0.05/1000 m = 5 × 10^-5 m
Where radius r = 2.5 × 10^-5 m
Density = 1200 kg/m^3
Area of a sphere = 4πr^2
A = 4 × π× (2.5 × 10^-5)^2
A = 7.8 × 10^-9 m^2
Volume V = 4/3πr^3
V = 4/3 × π × (2.5 × 10^-5)^3
V = 6.5 × 10^-14 m^3
Since density = mass/ volume
Make mass the subject of formula
Mass = density × volume
Mass = 1200 × 6.5 × 10^-14
Mass M = 7.9 × 10^-11 kg
Using the formula
V = sqrt( 2Mg/ pCA)
Where
g = 9.81 m/s^2
M = mass = 7.9 × 10^-11 kg
p = density = 1200 kg/m3
C = drag coefficient = 24
A = area = 7.8 × 10^-9m^2
V = terminal velocity
Substitute all the parameters into the formula
V = sqrt[( 2 × 7.9×10^-11 × 9.8)/(1200 × 24 × 7.8×10^-9)]
V = sqrt[ 1.54 × 10^-9/2.25×10-4]
V = 6.9×10^-6 m/s
V = 6.9 × 10^-4 cm/s
A multi-plate clutch is to transmit 12 kW at 1500 rev/min. The inner and outer radii for the plates are to be 50 mm and 100 mm respectively. The maximum axial spring force is restricted to lkN. Calculate the necessary number of pairs of surfaces if ll = 0-35 assuming constant ‘vyear. What will be the necessary axial force?
Answer:
The uniform pressure for the necessary axial force is W = 945 N
The uniform wear for the necessary axial force is W = 970.15 N
Explanation:
Solution
Given that:
r₁ = 0.1 m
r₂ = 0.05m
μ = 0.35
p = 12 N or kW
N = 1500 rpm
W = 1000 N
The angular velocity is denoted as ω= 2πN/60
Here,
ω = 2π *1500/60 = 157.07 rad/s
Now, the power transferred becomes
P = Tω this is the equation (1)
Thus
12kW = T * 157.07 rad/s
T = 76.4 N.m
Now, when we look at the uniform condition, we have what is called the torque that is frictional which acts at the frictional surface of the clutch dented as :
T = nμW R this is the equation (2)
The frictional surface of the mean radius is denoted by
R =2/3 [(r₁)³ - (r₂)³/(r₁)² - (r₂)²]
=[(0.1)³ - (0.05)³/[(0.1)² - (0.05)²]
R is =0.077 m
Now, we replace this values and put them into the equation (2)
It gives us this, 76. 4 N.m = n * 0.35* 1000 N * 0.077 m
n = 2.809 = 3
The number of pair surfaces is = 3
Secondly, we determine the uniform wear.
So, the mean radius is denoted as follows:
R = r₁ + r₂/ 2
=0.1 + 0.05/2
=0.075 m
Now, we replace the values and put it into the equation (2) formula
76. 4 N.m = n *0.35* 1000 N * 0.075 m
n= 2.91 = 3
Again, the number of pair surfaces = 3
However, for the uniform pressure with regards to the number of clutch plates is 3 we can derive the necessary axial force from the equation (2)
76. 4 N.m = 3 * 0.35 * W *0.077 m
W = 945 N
Also, for the uniform wear with regards to the number of clutch plates is 3 we can derive the necessary axial force from the equation (2)
76. 4 N.m = 3 * 0.35 * W *0.075 m
W = 970. 15 N
A flashed steam geothermal power plant is located where underground hot water is available as saturated liquid at 700 kPa. The well head pressure is 600 kPa. The
flashed steam enters a turbine at 500 kPa and expands to 15 kPa, when it is condensed. The flow rate from the well is 29.6 kg/s. determine the power produced in
kW.
Answer:
The power produced by the turbine is 74655.936 kW.
Explanation:
A turbine is a device that operates at steady-state. Let suppose that turbine does not have heat interactions with surroundings, as well as changes in potential and kinetic energies are neglictible. Power output can be determined by First Law of Thermodynamics:
[tex]-\dot W_{out} + \dot m \cdot (h_{in}-h_{out}) = 0[/tex]
[tex]\dot W_{out} = \dot m\cdot (h_{in}-h_{out})[/tex]
Let suppose that water enters as saturated vapor and exits as saturated liquid. Specific enthalpies are, respectively:
[tex]h_{in} = 2748.1\,\frac{kJ}{kg}[/tex]
[tex]h_{out} = 225.94\,\frac{kJ}{kg}[/tex]
The power produce by the turbine is:
[tex]\dot W_{in} = \left(29.6\,\frac{kg}{s} \right)\cdot \left(2748.1\,\frac{kJ}{kg} - 225.94\,\frac{kJ}{kg} \right)[/tex]
[tex]\dot W_{in} = 74655.936\,kW[/tex]
A 1000 mm wide steel sheet made of C35 is normalized by cold rolling 10 mm thick
deformed to 5 mm. The rollers, 600 mm in diameter, run at a peripheral speed of 0.12 m/s.
The deformation efficiency is 55%.
Find out:
a) the roller force
b) the roller torque
c) the performance on the pair of rollers.
Answer:
a. 20.265 MN
b. 0.555 MNm
c. 403.44 KW
Explanation:
Given:-
- The width ( w ) = 1000 mm
- Original thickness ( to ) = 10 mm
- Final thickness ( t ) = 5 mm
- The radius of the rollers ( R ) = 600 mm
- The peripheral speed of the roller ( v ) = 0.12
- Deformation efficiency ( ε ) = 55%
Find:-
a) the roller force ( F )
b) the roller torque ( T )
c) the performance on the pair of rollers. ( P )
Solution:-
- The process of flat rolling entails a pair of compressive forces ( F ) exerted by the rollers on the steel sheet that permanently deforms.
- The permanent deformation of sheet metal is seen as reduced thickness.
- We will assume that the compressive force ( F ) acts normal to the point of contact between rollers and metal sheet.
- The roll force ( F ) is defined as:
[tex]F =L*w*Y_a_v_g[/tex]
Where,
L: The projected length of strip under compression
Y_avg: The yielding stress of the material = 370 MPa
- The projected length of strip under compression is approximated by the following relation:
[tex]L = \sqrt{R*( t_o - t_f )} \\\\L = \sqrt{0.6*( 0.01 - 0.005 )} \\\\L = 0.05477 m[/tex]
- The Roll force ( F ) can be determined as follows:
[tex]F = (0.05477)*(1 )*(370*10^6 )\\\\F = 20.265 MN[/tex]
- The roll torque ( T ) is given by the following relation as follows:
[tex]T = \frac{L}{2} * F\\\\T = \frac{0.05477}{2} * 20.265\\\\T = 0.555 MNm[/tex]
- The rotational speed of the rollers ( N ) is determined by the following procedure:
[tex]f = \frac{v}{2\pi* R} = \frac{0.12}{2*\pi 0.6} = 0.03181818 \frac{rev}{s} \\\\N = f*60 = 1.9090 rpm[/tex]
- The power consumed by the pair of rollers ( P ) is given by:
[tex]P = \frac{2\pi * F * L * N}{e*60,000} KW \\\\P = \frac{2\pi * ( 20.265*10^6) * (0.05477) * (1.90909 ) }{60,000*0.55} KW\\\\P = 403.44 KW[/tex]
Answer every question of this quiz
Please note: you can answer each question only once.
Which number shows the intake valve?
OK
I'd say number 4, number 3 looks like an exhaust valve
The thrust F of a screw propeller is known to depend upon the diameter d,speed of advance \nu ,fluid density p, revolution per second N, and the coefficient of viscosity μ of the fluid. Determine the dimensions of each of the variables in terms of L,M,T,and find an expression for F in terms of these quantities
Answer:
screw thrust = ML[tex]T^{-2}[/tex]
Explanation:
thrust of a screw propeller is given by the equation = p[tex]V^{2}[/tex][tex]D^{2}[/tex] x [tex]\frac{ND}{V}[/tex]Re
where,
D is diameter
V is the fluid velocity
p is the fluid density
N is the angular speed of the screw in revolution per second
Re is the Reynolds number which is equal to puD/μ
where p is the fluid density
u is the fluid velocity, and
μ is the fluid viscosity = kg/m.s = M[tex]L^{-1}[/tex][tex]T^{-1}[/tex]
Reynolds number is dimensionless so it cancels out
The dimensions of the variables are shown below in MLT
diameter is m = L
speed is in m/s = L[tex]T^{-1}[/tex]
fluid density is in kg/[tex]m^{3}[/tex] = M[tex]L^{-3}[/tex]
N is in rad/s = L[tex]L^{-1}[/tex][tex]T^{-1}[/tex] =
If we substitute these dimensions in their respective places in the equation, we get
thrust = M[tex]L^{-3}[/tex][tex](LT^{-1}) ^{2}[/tex][tex]L^{2}[/tex][tex]\frac{T^{-1} L}{LT^{-1} }[/tex]
= M[tex]L^{-3}[/tex][tex]L^{2}[/tex][tex]T^{-2}[/tex]
screw thrust = ML[tex]T^{-2}[/tex]
This is the dimension for a force which indicates that thrust is a type of force