Answer:
a) What is the surface temperature, in °C, after 400 s?
T (0,400 sec) = 800°C
b) Yes, the surface temperature is greater than the ignition temperature of oak (400°C) after 400 s
c) What is the temperature, in °C, 1 mm from the surface after 400 s?
T (1 mm, 400 sec) = 798.35°C
Explanation:
oak initial Temperature = 25°C = 298 K
oak exposed to gas of temp = 800°C = 1073 K
h = 20 W/m².K
From the book, Oak properties are e=545kg/m³ k=0.19w/m.k Cp=2385J/kg.k
Assume: Volume = 1 m³, and from energy balance the heat transfer is an unsteady state.
From energy balance: 
Initial temperature wall = 
Surface temperature = T
Gas exposed temperature = 
Answer:
modulus =3.97X10^6 Ib/in^2, Poisson's ratio = 0.048
Explanation:
Modulus is the ratio of tensile stress to tensile strain
Poisson's ratio is the ratio of transverse contraction strain to longitudinal extension strain within the direction of the stretching force
And contraction occur from 0.6 in x 0.6 in to 0.599 in x 0.599 in while 2 in extended to 2.007, with extension of 0.007 in
Answer:
Less intervention of humans.
Explanation:
This fact illustrate that less intervention of human in the production is the main cause for increase in productivity because use of machinery completed the work in less time as compared to the use of human labour. In many industries, machines takes the place of humans which increases the production of products but at the same time, increase the unemployment rate in the society. Making the whole industry on automation can increase the productivity of products in less time.
The Engineers in Russia invented a new way to create colorful art with constructivist art.
<h3>
What is constructivist art?</h3>
Constructivist art was aimed to reflect modern industrial society and urban space in art. It uses industrial production forms and modest materials for its art production.
The constructivists proposed to replace traditional art's with a focus on construction as Engineers rather than a painter.
Therefore, the Engineers in Russia invented a new way to create colorful art with constructivist art using construction.
Learn more on constructivist here,
brainly.com/question/14054863
Answer and Explanation:
The DC motor has coils inside it which produces magnetic field inside the coil and due to thus magnetic field an emf is induced ,this induced emf is known as back emf. The back emf always acts against the applied voltage. It is represented by 
The back emf of the DC motor is given by 
Here N is speed of the motor ,P signifies the number of poles ,Z signifies the the total number of conductor and A is number of parallel paths
As from the relation we can see that back emf and speed ar dependent on each other it means back emf limits the speed of DC motor
