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2 years ago

The force of impact is

1 answer:

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In mechanics, an impact is a high force or shock applied over a short time period when two or more bodies collide. Such a force or acceleration usually has a greater effect than a lower force applied over a proportionally longer period.

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Atmospheric air at 25 °C and 8 m/s flows over both surfaces of an isothermal (179C) flat plate that is 2.75m long. Determine the

vekshin1

Answer:

Re=100,000⇒Q=275.25 $\frac{W}{m^2}$

Re=500,000⇒Q=1,757.77 $\frac{W}{m^2}$

Re=1,000,000⇒Q=3060.36 $\frac{W}{m^2}$

Explanation:

Given:

For air $T_∞$ =25°C ,V=8 m/s

For surface $T_s$ =179°C

L=2.75 m ,b=3 m

We know that for flat plate

$Re$ ⇒Laminar flow

$Re>30\times10^5$ ⇒Turbulent flow

So this is case of laminar flow

$Nu=0.664Re^{\frac{1}{2}}Pr^{\frac{1}{3}}$

From standard air property table at 25°C

Pr= is 0.71 ,K=26.24 $\times 10^{-3}$

So $Nu=0.664\times 100,000^{\frac{1}{2}}\times 0.71^{\frac{1}{3}}$

Nu=187.32 ( $\dfrac{hL}{K_{air}}$ )

187.32= $\dfrac{h\times2.75}{26.24\times 10^{-3}}$

⇒h=1.78 $\frac{W}{m^2-K}$

heat transfer rate =h $(T_∞-T_s)$

=275.25 $\frac{W}{m^2}$

So this is case of turbulent flow

$Nu=0.037Re^{\frac{4}{5}}Pr^{\frac{1}{3}}$

$Nu=0.037\times 500,000^{\frac{4}{5}}\times 0.71^{\frac{1}{3}}$

Nu=1196.18 ⇒h=11.14 $\frac{W}{m^2-K}$

heat transfer rate =h $(T_∞-T_s)$

=11.14(179-25)

= 1,757.77 $\frac{W}{m^2}$

So this is case of turbulent flow

$Nu=0.037Re^{\frac{4}{5}}Pr^{\frac{1}{3}}$

$Nu=0.037\times 1,000,000^{\frac{4}{5}}\times 0.71^{\frac{1}{3}}$

Nu=2082.6 ⇒h=19.87 $\frac{W}{m^2-K}$

heat transfer rate =h $(T_∞-T_s)$

=19.87(179-25)

= 3060.36 $\frac{W}{m^2}$

7 0

3 years ago

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klemol [59]

Answer:

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6 0

3 years ago

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Special considerations must be given to systems using liquid hydrogen for fuel because of: A. Liquid hydrogen's low density B. L

vitfil [10]

Answer:

D.All of the above

Explanation:

Properties of hydrogen:

1.It is lighter than air.It has density about 0.089 g/L.

2.Hydrogen rapidly change from liquid state to gas,so special protection is required to protect it.

3.It is highly flammable gas.

4.Liquid form of hydrogen exits at -432 F .This is very low temperature so special protection requires to keep it in liquid form.

6 0

3 years ago

82 Determine the magnitude of force P needed to start

pantera1 [17]

Answer:

Magnitude of force P needed to start

towing the 40-kg crate = 140.14 N

Location of the resultant normal force acting on the crate, measured from point A = 500

Explanation:

The explanation for this question is given in the attachment below.

4 0

3 years ago

Determine the carburizing time necessary to achieve a carbon concentration of 0.30 wt.% at a position of 4 mm into an iron-carbo

Alex17521 [72]

The carburizing time necessary to achieve a carbon concentration is 31.35 hours

<h3>How to find the Carburizing Time?</h3>

To determine the carburizing time necessary to achieve the given carbon concentration, we will use the equation:

(Cs - Cx)/(Cs - C0) = ERF(x/2√Dt)

where;

Cs is Concentration of carbon at surface = 0.90

Cx is Concentration of carbon at distance x = 0.30

Distance x = 4 mm = 0.004 m

C0 is Initial concentration of carbon = 0.10

ERF() = Error function at the given value

D = Diffusion of Carbon into steel

t = Time necessary to achieve given carbon concentration ,

Thus, plugging in the relevant values gives;

(Cs - Cx)/(Cs - C0) = (0.9 - 0.3)/(0.9 - 0.1)

= 0.6/0.8 = 0.75

now, ERF(z) = 0.75 and as such using ERF table, we can say that;

Z = 0.814. Thus;

(x/2√Dt) = 0.81

Using the table of diffusion data, we have;

At a temperature of (1100°C) or 1373 K, we have;

D = 5.35 × 10⁻¹¹ m²/sec.

Calculating the carbonizing time by using the equation z = (x/2√Dt);

where;

t is carbonizing time

Thus;

0.814 = (0.004/(2 × √5.35 × 10⁻¹¹ × √t))

0.814 = 0.004 /(1.4628 × 10⁻⁵ × √t)

0.814 × 1.4628 × 10⁻⁵ × √t = 0.004

1.19072 × 10⁻⁵ × √t = 0.004

√t = 0.004/(1.19072 × 10⁻⁵)

√t = 335.93

t = 112848.96 seconds

Converting to hours gives;

t = 112848.96/3600

t = 31.35 hours

Therefore, the carburizing time necessary to achieve a carbon concentration is 31.35 hours

Read more about Carburizing Time at; brainly.com/question/13031810

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2 years ago