1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
Vera_Pavlovna [14]
3 years ago
6

A bridge to be fabricated of steel girders is designed to be 500 m long and 12 m wide at ambient temperature (assumed 20°C). Exp

ansion joints will be provided to compensate for the change in length in the girders as the temperature varies. Each expansion joint can compensate for a maximum of 20 mm of change in length. From historical records it is estimated that the minimum and maximum temperatures in the region will be -35°C and 40°C, respectively. Determine (a) the minimum number of expansion joints required and (b) the length that each bridge section should be fabricated. The coefficient of thermal expansion α=12(10-6)/C for steel.
Physics
1 answer:
andrew-mc [135]3 years ago
4 0

Answer:

23

21.7391304348 m

Explanation:

L = Initial length = 500 m

\Delta T = Change in temperature = 40-(-35)

\alpha = Coefficient of thermal expansion = 12\times 10^{-6}\ /^{\circ}C

Change in length is given by

\Delta L=L\alpha \Delta T\\\Rightarrow \Delta L=500\times 12\times 10^{-6}\times (40-(-35))\\\Rightarrow \Delta L=0.45\ m

The change in length is 0.45 m

The number of joints would be

n=\dfrac{0.45}{0.02}\\\Rightarrow n=22.5\\\Rightarrow n\approx 23

The number of joints is 23

Each bridge section length would be

\dfrac{L}{n}=\dfrac{500}{23}=21.7391304348\ m

The length of each bridge section would be 21.7391304348 m

You might be interested in
Steam flows steadily through an adiabatic turbine. The inlet conditions of the steam are 4 MPa, 500◦C, and 80 m/s, and the exit
Cerrena [4.2K]

Answer:

a) ΔEC=-23.4kW

b)W=12106.2kW

c)A=0.01297m^2

Explanation:

A)

The kinetic energy is defined as:

\frac{m*vel^2}{2} (vel is the velocity, to differentiate with v, specific volume).

The kinetic energy change will be: Δ (\frac{mvel^2}{2})=\frac{m*vel_2^2}{2}-\frac{m*vel_1^2}{2}

Δ (\frac{mvel^2}{2})=\frac{m}{2}*(vel_2^2-vel_1^2)

Where 1 and 2 subscripts mean initial and final state respectively.

Δ(\frac{mvel^2}{2})=\frac{12\frac{kg}{s}}{2}*(50^2-80^2)\frac{m^2}{s^2}=-23400W=-23.4kW

This amount is negative because the steam is losing that energy.

B)

Consider the energy balance, with a neglective height difference: The energy that enters to the turbine (which is in the steam) is the same that goes out (which is in the steam and in the work done).

H_1+\frac{m*vel_1^2}{2}=H_2+\frac{m*vel_2^2}{2}+W\\W=m*(h_1-h_2)+\frac{m}{2} *(vel_1^2-vel_2^2)

We already know the last quantity: \frac{m}{2} *(vel_1^2-vel_2^2)=-Δ (\frac{mvel^2}{2})=23400W

For the steam enthalpies, review the steam tables (I attach the ones that I used); according to that, h_1=h(T=500C,P=4MPa)=3445.3\frac{kJ}{kg}

The exit state is a liquid-vapor mixture, so its enthalpy is:

h_2=h_f+xh_{fg}=289.23+0.92*2366.1=2483.4\frac{kJ}{kg}

Finally, the work can be obtained:

W=12\frac{kg}{s}*(3445.3-2438.4)\frac{kJ}{kg} +23.400kW)=12106.2kW

C) For the area, consider the equation of mass flow:

m=p*vel*A where p is the density, and A the area. The density is the inverse of the specific volume, so m=\frac{vel*A}{v}

The specific volume of the inlet steam can be read also from the steam tables, and its value is: 0.08643\frac{m^3}{kg}, so:

A=\frac{m*v}{vel}=\frac{12\frac{kg}{s}*0.08643\frac{m^3}{kg}}{80\frac{m}{s}}=0.01297m^2

Download pdf
7 0
3 years ago
What is the basic unit of matter? atom cell bacterium molecule Description
Zielflug [23.3K]
The atom is the most basic unit of matter 

6 0
3 years ago
Read 2 more answers
All the interconnected paths of energy flowing from species to species in an ecosystem is called a
MAXImum [283]
D is the correct answer .
4 0
3 years ago
Read 2 more answers
What is this ???????????
babymother [125]
A, something to remember is that if the numbers are even the answer too will be even. Every time hope this helps :>
8 0
3 years ago
Read 2 more answers
If Pressure = 1000 Pa and Area = 0.2 m square, then Force
Maksim231197 [3]

Here

Pressure=1000Pa

Area=0.2m Square

Force=?

Now,,

Pressure =force / Area

1000=force/0.2

force=1000/0.2

Therefore,Force=5000N

3 0
3 years ago
Other questions:
  • You are standing at a subway platform when a subway passes, sounding its whistle. If you observe the whistle to be at 12750Hz wh
    5·1 answer
  • Which method is not a technique currently used by ocean scientists to map the topography of the ocean floor?
    13·1 answer
  • An excited hydrogen atom releases an electromagnetic wave to return to its normal state. You use your futuristic dual electric/m
    11·1 answer
  • As a 15000 kg jet plane lands on an aircraft carrier, its tail hook snags a cable to slow it down. The cable is attached to a sp
    14·1 answer
  • A crow drops .11 -kg clam onto a rocky beach from a height of 9.8 m. What is the kinetic energy of the clam when it is 5.0 m abo
    9·1 answer
  • ANSWER ASAP!!!If a wave machine produces 10 waves in 2 seconds, what is the frequency of the machine in Hertz?
    9·1 answer
  • What happens to your kinectic energy when your gravitational potential energy decreases?
    10·1 answer
  • Why are the alkali metals likely to react with group 17 elements?
    7·1 answer
  • Two objects are placed on a scale so that it balances. One object weighs 5 N and is placed 0.5 m from the fulcrum of the scale.
    13·1 answer
  • The layers in a high-mass star occur in order of:________
    5·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!